WO2015165884A1 - Electronic drum interface - Google Patents

Abstract

A device is disclosed for acquiring and processing signals from one or more sensors embedded in a percussion membrane. The sensors embedded in a percussion membrane are operationally connected to a percussion membrane. The device converts the sensor signals to input signals for a drum peripheral instrument. The device may output industry standard-compatible signals for input into a general purpose computer, a smartphone, a MIDI player, or the like. The device may output an emulated piezo signal for input into a drum brain. The device is particularly suitable for acquiring and processing signals from sensors embedded in a percussion membrane that are coated or printed onto a drumhead or onto a surface vibrationally connected to a drumhead.

Description

ELECTRONIC DRUM INTERFACE

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates generally to an electronic interface for acquiring and processing signals from sensors that are embedded in a vibrating membrane, and more particularly for acquiring and processing signals from sensors vibrationally connected to a percussion membrane.

2. Description of the Related Art

[0002] US Patent No. 6,271,458 Bl discloses an electronic drum using a piezo element for triggering. This patent discloses an electronic interface for acquiring and processing the piezo signal.

[0003] US Patent No. 6,815,602 B2 discloses an electronic percussion instrument with a variable resistive switch that is impact position-dependent. The percussion instrument also contains a piezo electric element. The patent discloses an electronic interface for acquiring and processing signals from the variable resistive switch and from the piezo electric element.

[0004] M y earlier patent application WO2012/122608 Al discloses a drum head having one or more of sensors embedded in a percussion membrane. The sensors are applied to the drum head using a coating or a printing technique. The sensors produce a signal that is different in character from that of a piezo electric element that is in indirect contact with a drumhead, or a variable resistive switch. The signal produced by the sensors may be used for a variety of applications, including triggering, tuning and direct amplification.

[0005] Existing electronic drum modules ("drum brains") are specifically designed for processing signals of the type produced by piezo electric elements that are in indirect contact with a drumhead. [0006] Thus, there is a need for an electronic interface for acquiring and processing signals from sensors embedded in a percussion membrane. There is a particular need for processing such signals so as to produce a signal that is compatible with an industry standard. There is a further need for conditioning and optionally processing such signals to make them suitable as input signals of a PA system. There is a further need for processing such signals so as to make them suitable for input into an off-the-shelf drum brain.

[0007] BRIEF SUMMARY OF THE INVENTION

The present invention addresses these problems by providing a device for acquiring signals from one or more sensors embedded in a percussion membrane, said membrane defining an x-y plane, and converting said signals to input signals for a drum peripheral instrument, said device comprising: a. one or more signal acquisition circuits for acquiring analog signals comprising signals caused by a strain within the x-y plane of the percussion membrane from the one or more sensors; b. one or more conditioning circuits for conditioning the analog signals acquired in the one or more acquisition circuits; c. means for inputting the conditioned signals obtained in b. into a PA system or an analog-to-digital converter. [0008] The device may further comprise an analog-to-digital converter for converting the conditioned analog signals obtained in b., and a processor for processing the digital signals so obtained.

[0009] The device may further comprise a digital/analog converter, and/or outlets for one or more of (i) the unprocessed digital signal; (ii) a digital signal processed to be compatible with an industry standard; and (iii) an analog form of a processed signal.

BRIEF DESCRIPTION OF THE FIGURES

[0010] Figure 1 A is a perspective view of a drumhead having six capacitive sensors embedded in a percussion membrane. Figure IB is a top view of the drumhead of Figure 1A. [0011] Figure 2 A is a perspective view of a drumhead having six resistive sensors embedded in a percussion membrane. Figure 2B is a top view of the drumhead of Figure 2A.

[0012] Figure 3 A is a schematic representation of a portion of a drumhead, showing four sensors and a number of impact locations. Figure 3B is a representation of five signals as may be acquired from Sensor S4 of the drumhead of Figure 3A in response to equivalent impacts at five different impact locations.

[0013] Figure 4 is a schematic representation of a device according to the invention.

[0014] Figure 5 is a schematic representation of an alternate device according to the invention.

[0015] Figure 6 is a schematic representation of a device according to the invention as used in direct amplification.

[0016] Figure 7 is a schematic representation of a device comprising an external computer running applications software. DETAILED DESCRIPTION OF THE INVENTION

[0017] The following is a detailed description of the invention.

Definitions

[0018] The term "drum" as used herein refers to any percussion instrument and any other musical instrument comprising a percussion membrane, such as a torn, a snare drum, a bass drum, a banjo, a xylophone, an acoustic cymbal, a cow bell, a timpani, a conga drum, a cajon drum, and the like. The term encompasses pads used for muting or practice, mesh heads, electronic pads, electronic cymbals, and the like.

[0019] The term "vibration" as used herein refers to any periodic deformation of a body producing sound waves. [0020] The terms "vibrationally connected" and "vibrational connection" as used herein refer to sensors embedded in a percussion membrane that are positioned so that a vibration of a percussion membrane causes a strain in a material to which the sensors are physically connected. The sensors may be physically connected to the percussion membrane itself, or to a surface that is caused to vibrate when the percussion membrane vibrates, for example by being located just underneath the percussion membrane or on a surface mechanically coupled to the vibrating surface.

[0021] The term "percussion membrane" refers to any surface used in a musical instrument by striking it with a body part (hand, foot, elbow etc.) or an instrument (drumstick, brush, mallet, etc.). For convenience the term "drumhead" is frequently used in this text. The reader should bear in mind that this term is generally used in this document synonymous to the term percussion membrane. The percussion membrane can be made of a variety of materials, such as a polymer, leather, wood, or metal.

[0022] The percussion membrane defines a plane, which is referred to herein as an "x-y plane." Percussion membranes such as drum heads are generally flat, and the x-y plane defined by such a percussion membrane is also flat. In the case of a cymbal or a cow bell the x-y plane defined by the percussion membrane is in general not flat. Nevertheless, the skilled person will have no difficulty identifying the x-y plane defined by the percussion membrane.

[0023] The term "sensor embedded in a percussion membrane" as used herein refers to any sensor that is associated with or applied to the membrane so it produces a signal in response to a strain, deformation or movement in the x-y plane defined by the percussion membrane. In specific embodiments the material is in the form of a sheet, for example a drum skin. The sensor may be physically connected to the sheet with an adhesive, by heat welding, etc. In a particular embodiment the sensor comprises a pattern of conductive material that is applied to the sheet material using a coating or printing technique.

[0024] Any technique resulting in a pattern of conductive material may be used. Examples of suitable coating techniques include any coating technique known to the skilled person in semiconductor manufacturing, such as sputtering, chemical vapor deposition, physical vapor deposition, atomic layer deposition, plasma coating, spin coating, slight bead coating, reverse gravure, curtain coating, spray coating, blade coating and the like. Examples of suitable printing techniques include laser jet printing; 3D printing; bubble jet printing; screen printing; off-set printing, roll to roll printing, aerosol jet printing, flexographic printing, (roto-) gravure printing, lithographic printing, micro-contact printing, photolithography, electrophotography, nano-lithography, pad printing, evaporation printing, PDIM (pre-deposited images in metal), stamping and the like. Transfer printing, and similar techniques, which transfer solid layers from a carrier to a substrate, are also considered printing. Particularly preferred are the sensors disclosed in WO 2012/122608 Al, the disclosures of which are incorporated herein by reference. Other types of strain gauges, such as coated foil strain gauges and piezo resistors are also suitable for use in the present invention. [0025] In case the percussion membrane is itself made of a conductive material, for example metal, the conductive pattern is separated from the percussion membrane by an electrically insulating material, for example a thin sheet of polymer material. The electrically insulating material could be printed or coated, but any application technique is suitable.

[0026] Other types of sensors that respond to a movement, such as a vibration, of a membrane to which it is applied may be used. Examples include accelerometers, nano- generators, and motion sensitive capacitors.

[0027] The term "sensor" as used herein encompasses membrane materials and film materials exhibiting changes in their electric properties in response to deformation, such as stretch. An example of such material is PVDF Piezoelectric Film. Similarly an optical fiber can be embedded in a material that is subjected to strain. Stretching of the material results in a corresponding stretch /bending of the optical fiber, which can be measured as a change in the time needed for an optical pulse to travel from one end of the fiber to the opposite end.

[0028] The term "signal acquisition circuit" as used herein refers to electronic circuits designed for acquiring signals generated by the embedded sensors. In general an acquisition circuit serves to convert changes in a physical characteristic of the sensor into an electronic signal. For example, strain in the percussion membrane may cause a change in the ohmic resistance of a resistive sensor. An acquisition circuit converts this change in ohmic resistance into a voltage change, for example. In case of a capacitive sensor, strain in the percussion membrane may cause a change in the capacitance of the sensor. An acquisition circuit may convert the change in capacitance into a voltage change, for example. [0029] Sensors made of a piezoelectric material directly produce a voltage in response to a vibration of the percussion membrane. Other types of signals, such as the travel time of an electric pulse in an optical fiber, can be converted into an electronic signal by methods well known to the skilled person.

[0030] The term "conditioning" as used herein in reference to signals refers to any form of electronic modification of the electronic signal acquired by the acquisition circuit for the purpose of making the signal suitable for signal processing. It will be understood that a raw signal obtained by the acquisition circuit may be too strong or too weak for further processing; it may be contaminated with unwanted noise; it may suffer from unwanted distortions, and the like. The purpose of conditioning is to remove unwanted contaminant signals from the raw signal, and to put it in a form that can be handled by the next stage of signal processing. The conditioning circuit may comprise one or more amplifiers, for example a low gain amplifier and a high gain amplifier; one or more filters; and the like.

[0031] The term "latency" refers to the time lapse between the generation of a signal and the generation of a physical effect associated with the signal. The latency of the device of the present invention is defined as the time lapse between the impact of a percussion membrane and the generation of an output signal of the device. The latency is of particular importance when the device generates an output signal that is time critical, for example to produce a audio or visual feedback, a sound wave, to play a MIDI, serve as a trigger signal to start a program, and the like. [0032] Present day electronic drums rely on either a piezo electric element or on an impact position dependent resistive switch for detecting an impact on an electronic drum head. The former is exemplified in US Patent 6,271,458 Bl ; the latter in US Patent No. 6,815,602 B2. Electronic modules have been developed that capture the signal of a piezo electric element and convert it to a sound emulating the sound of an acoustic drum. Electronic modules of this type are commonly referred to as drum brains. Generally the sensors used in prior art systems are designed and configured to detect vibrations of a percussion membrane in a direction generally perpendicular to the plane of the percussion membrane, i.e., the z-direction.

Movements in the x-y plane of the percussion membrane are not detected, and commercially available drum brains are not equipped to handle signals that include information relating to movements in the x-y plane of the percussion membrane. Piezo triggers are typically separated from the percussion membrane by a muffling element, for example a disc of foam rubber, to filter out all but the most pronounced z-direction vibrations.

[0033] WO 2012/122608 Al discloses drum heads having multiple sensors embedded in a percussion membrane. The sensors provide a rich set of data in response to an impact permitting determination of the location of the impact, the time of the impact, the frequency and the amplitude of the resulting vibration. The device of the present invention is designed to make use of the richness of these data. As a result of being embedded in the percussion membrane these sensors generate signals relating to movements, displacements, translations, rotations and shape variations within the x-y plane of the percussion membrane, as well as signals relating to movements perpendicular to the x-y plane of the percussion membrane. Movements at an angle to the x-y plane other than a 90° angle can be seen as comprising a component in the x-y plane and a component in the z-direction.

[0034] As compared to prior art drum sensors, sensors embedded in a percussion membrane produce signals that are very information-rich, but also very complex. Due to the richness of information the signals can be used in a variety of ways, for example in triggering, tuning, direct amplification, and the like. When a percussion membrane in rest is tensioned, compressed or bent, a static tension or compression force of a certain magnitude is present in the membrane. This static tension or compression exerts a proportional strain in the x-y plane of the percussion membrane, which causes a proportional elongation of the percussion membrane, resulting in a change in membrane thickness related to its elongation. Typically the thickness of an elongated membrane is proportionally reduced with the applied amount of strain. It will be obvious to one skilled in the art that the static strain condition of a percussion membrane can therefore be measured statically by at least one strain detecting sensor embedded in said percussion membrane if combined with suitable acquisition hardware providing information of the x-y component.

[0035] For tuning purposes the static signal acquisition and processing of the x-y component in the signal provides an indication of a local tension amount, or a tension amount distribution, in the percussion membrane. The static tension distribution in a percussion membrane provides an indication of the sound that it will generate when vibrating

dynamically. Tuning a drumhead is a time consuming matter, as monitoring the effect of changes in tension on one tuning location on the other tensioning locations and the overall tension distribution is impossible with means available today. A particular benefit of a device that is capable of acquisition of the x-y component of signals from embedded sensors is that the tuning state of the membrane can be known, without further need to analyze the sound generated by the membrane when vibrating. In such manner a drum can be tuned without the need for agitating its percussion membrane, because a full insight in the local and or overall tension distribution at the one or more tensioning points is provided by the x-y component in the signal. This is an advantage that speeds-up the tuning process and allows tuning the drum in silence. The analysis of sequential static sensor signal measurements over time provides insight in variations of static tension within the analyzed time span. The analysis of sequential static sensor signal measurements over time is particularly useful for tuning purposes to provide insight in the changes of local tension at the one or more tensioning points as a consequence of a tuning action and / or to provide insight in the changes of the overall tension distribution of the percussion membrane as a consequence of said tuning action. An interface device conceived to determine the pitch of a percussion surface by acquiring the x-y component, is for example particularly useful when applied in a tympani drum, as it provides tuning feedback about the pitch or tension of the percussion membrane, or about the changes thereof as a consequence of the tuning action exerted by a variation of the pedal position of the tympani, when the percussion membrane is in rest and when it is vibrating. [0036] When the aforementioned percussion membrane is vibrating, further deformation will cause a displacement of the membrane out of the x-y plane, with movement components in the z-direction. When a percussion membrane is struck, acoustic waves pass through the membrane at high velocity, causing compression and elongation of the membrane in the x-y plane along the travel path of the waves, causing a complex deformation of the membrane in the z-direction and in the x-y plane. Acoustic waves may be observed by means of strain sensors embedded in the percussion membrane of which the longitudinal and/or transverse shear components can be detected when the waves propagate through the x-y plane at the sensor's location. A particular advantage of a device that is designed to observe dynamic strain variations in the x-y plane of the sensor signal in a given time frame, is that the additional x-y component in the signal's content allows to detect an impact event on the percussion membrane more accurately in said time frame. This is because a sudden increase of the strain in the x-y plane provides an indication of a sudden increase of stored energy in the membrane as a consequence of an impact force exerted upon it. For triggering purposes, a device enabled to analyze the x-y component of the signal, in addition to the z-component, can therefore perform more robust impact detection algorithms, resulting in a reduced number of false positives or false negatives.

[0037] Another interesting benefit of such a device is that it can detect an impact on a percussion membrane by analyzing the strain variations of the x-y plane, which result from high frequency waves that propagate through the percussion membrane immediately after the moment of impact. The x-y components in such high frequency waves provide a very early indication of an impact event. The strain caused by such waves in the x-y plane is typically present in the sensor signal as a high frequency x-y component, which cannot be detected with the sensors or drum brains used to date for drum triggering purposes. These waves are difficult to detect by observing the z- component alone, because they may cause less of a deformation in the z-axis direction, resulting in lower amplitudes of the z component than the x-y component. A device designed to detect these high frequency waves in the x-y plane, allows a reduced impact detection latency compared to currently used devices, because such a device is enabled to trigger on an impact event itself. Such a device can trigger upon the moment that an impact medium makes surface contact with the percussion membrane.

Looking at the z-component alone allows to trigger on the vibrations of said membrane which typically occurs right after the impact event, in other words, after the moment when the impact medium released contact with the surface of the membrane. At the moment of impact between a stick and a drumhead, the energy transferred by contact between stick and the percussion membrane causes waves to travel at high speed through the membrane, which induce strain the x-y plane which is present in the embedded sensor signal before the stick is released from the surface of the membrane and an audible resonation is generated by the percussion membrane. Being able to detect the x-y component of a wave earlier, where amplitude of the z-component is typically low, allows for earlier impact detection and reduced latency. However to benefit from the advantages described above, an adapted device is required that is designed and configured to analyze such complex signal content correctly. [0038] Electronic drum brains available to date are not capable of processing signals of this complexity.

[0039] In its broadest aspect the present invention relates to a device for acquiring signals from one or more sensors embedded in a percussion membrane and converting said signals to input signals for a drum peripheral instrument, said device comprising: A. one or more signal acquisition circuits for acquiring analog signals comprising signals caused by strain within the x-y plane of a percussion membrane from the one or more sensors;

B. one or more conditioning circuits for conditioning the analog signals acquired in the one or more acquisition circuits; C. means for inputting the conditioned signal obtained in B. into a PA system or an analog-to-digital converter.

[0040] The sensors embedded in the percussion membrane undergo changes in one or more physical characteristics as a result of vibrations in the percussion membrane. The acquisition circuit or circuits serve to convert these changes in physical characteristics into electronic signals. The type of acquisition circuit depends on the physical characteristic of the sensors. For example, Wheatstone Bridge circuits or Anderson Loop circuits may be used for acquiring signals from resistive sensors. Suitable acquisition circuits for capacitive and piezo sensors are disclosed in Liobe et al, "Ultra- low Overhead Signal Acquisition Circuit for Capacitive and Piezo Sensors" presented at the 51^st Midwest Symposium on Circuits and Systems, 2008, the disclosures of which are incorporated herein by reference.

[0041] The signals acquired by the signal acquisition circuits can be referred to as "raw signals" containing all information registered by the sensors, as well as unwanted noise produced by sources such as a power supply, electromagnetic interference, phantom signals, and the like. In general the percussion membrane comprises conductive traces and leads for acquiring signals from the sensors and for conducting the signals to the device. These traces and leads are themselves subject to the vibrations of the percussion membrane and to antenna effects, which may cause phantom signals.

[0042] The conditioning circuit or circuits generally serve to remove unwanted noise from the raw signals, and to adjust the signal strength to a range appropriate for the subsequent processing of the signals. Adjusting the signal strength may comprise amplification if the signal, and/or shielding to remove unwanted peaks that may overwhelm the electronics of a subsequent processing stage.

[0043] It is generally desirable to separate the acquired signals into an x-y component and a z-component. Depending on the use to be made of the signal, one of the two components may be discarded (e.g., removed by filtering) while the remaining component is processed in a manner appropriate for the desired use. In other embodiments both components are processed and used.

[0044] For example, the acquired signal may be used for direct amplification in a sound amplification system, for example a 'public address' (PA) system. For this application the z- component is of interest, because it is the z-component that produces sound. For this application the conditioning circuit may condition the signal by removing unwanted noise and phantom signals, pre-amplify the signal to produce a signal strength appropriate for a sound amplification system, shield unwanted peaks, and pass the conditioned signal to the sound amplification system, for example using an XLR connector. In this application the x-y component of the signal is unwanted, and may be removed by the conditioning circuits.

[0045] For tuning, by contrast, the x-y component of the signal is of particular interest. For this application it is desirable to separate the signal into its x-y and z components, and to process each component separately. It is possible to use just the z-component in for tuning, similar to a tuning protocol based on sound acquired by for example a microphone. Dynamic signal measurements are generally suited for such a tuning protocol. It is also possible to use just the x-y component in tuning, in which case the tuning protocol focuses on the strain in the percussion membrane. Static signal measurements are typically suited for such a tuning protocol. It is also possible to use both components in a tuning protocol. [0046] For triggering it is possible to use just the z component, as one would when triggering on a prior art piezo transducer, which is typically configured to only register the z component of a vibration. However, the x-y component contains information that is very valuable for more sophisticated forms of triggering. Vibrations in the x-y plane travel much faster than vibrations in the z direction. This property is valuable in determining the time and the location of a hit. The z component contains information relating to the amplitude of the vibration, which is a measure of the loudness of the sound. In the more sophisticated triggering applications both components are used.

[0047] The conditioned analog signal may be sent to a sound amplification system for direct amplification, equalizing, mixing, and so on, or it may be sent to an analog-to-digital converter for further digital processing. Separating the x-y component and the z component of the signal may be done by the conditioning circuits, as described above, or it may be done digitally after the analog-to-digital conversion. In the latter case this separation would generally be considered to be part of the signal processing. In a preferred embodiment the conditioning circuit comprises a form of filtering, for example to remove or attenuate higher frequency components from the raw sensor signal in order to prepare it for digital processing or direct amplification, equalizing, mixing and so on . [0048] In many embodiments the device comprises, as additional components

D. an analog-to-digital converter for converting the conditioned analog signal from B.; and

E. a processor for processing the digital signals produced in D. [0049] In an embodiment the device of the invention converts the digital signals to a digital form of drum brain compatible signals. In general this means that the digital signals are converted to a digital form of the type of signal generated by a piezo electric element. The device may further comprise a digital/analog converter, as most commercially available drum brains require an analog input signal. In an embodiment the device emulates a piezo electric signal, which can be input into a drum brain designed for processing piezo electric signals.

[0050] In an embodiment the drum peripheral instrument is a drum tuner. The tuner may be adapted to process the analog signals acquired by the one or more signal acquisition circuits. For this type of tuner the device may be provided with an outlet that outputs the analog signal produced by the signal acquisition circuit or circuits. [0051] In an alternate embodiment the tuner is adapted to process digital signals without prior processing. For this purpose the device may be provided with an outlet for signals output by the analog/digital converter. The signal may be processed off-board, for example in a computer or smartphone, in an app or plug-in software, or in a dedicated device such as a tuning device. In another embodiment the device is adapted to pre-process digital signals before hand-off to a tuner. For this purpose the device may be provided with an outlet for pre- processed digital signals. In an embodiment all functions (signal acquisition, signal processing and providing feedback to the user) are integrated in one device

[0052] Generally, tuning of a drum head comprises adjusting the tension of the drumhead by adjusting one or more tensioning rods or bolts (sometimes referred to as lugs) that pull on an annular ring surrounding the drumhead. The sensors embedded in a percussion membrane offer two different modes of tuning. In a first mode tuning comprises providing an impact to the drumhead, for example by beating with a drumstick. The impact causes the drumhead to vibrate. This vibration is detected by the sensors, and picked up by the signal acquisition circuits as an electrical signal, for example as an analog wave form. The wave form signal permits a determination of the frequencies present in the vibration spectrum. The signal may be converted from the time domain to the frequency domain using suitable methods and algorithms known to the skilled person, for example by using a transform of the Fourier Transform family, such as Fast Fourier Transform (FFT); Discrete Fourier Transform (DFT); Sparse Fourier Transform (SFT); or Short-Time Fourier Transform (STFT); a transform of the Hartley family, such as FHT or DHT; the wavelet transform family (FWT, DWT);

multiresolution analysis (MRA) or multiscale approximation (MSA), McAulay-Quatieri Analysis (MQ); Karhunen-Loeve Transform(KLT); and Autoregressive Spectral

Analysis(AR).

[0053] In general, the transform algorithm allows to create a power spectrum, optionally after filtering and/or windowing, in the time domain or the frequency domain. This power spectrum is used to derive data pertaining to phase, frequency, magnitude and partials. These data can be compared to target values to determine tuning instructions

[0054] In an alternate approach the frequency of the waveform itself can be analyzed. For example, the first half-wave time is a characteristic of the wave form that is directly related to the fundamental frequency of the vibration; see US Patent Application Publication No.

2010/0212475, the disclosures of which are incorporated herein by reference. Tuning aims to adjust the frequency of the vibration to correspond to the desired fundamental frequency, the desired amount of sustain and to a desired harmonic, inharmonic or overtone frequency near the perimeter of a particular drum. In addition, the drumhead should be tensioned evenly, so that impacts at any position on a concentric circle having the center of the drumhead as its center produce the same overtones. As each sensor produces its own wave form signal, both aspects of tuning can be accommodated. For example, a tuner receiving signals from all sensors may determine the sensor signal that deviates most from the desired frequency, and instruct the user to tighten or loosen the tensioning lug or lugs nearest the location of the corresponding sensor. The procedure may be repeated until all sensors produce a signal of the desired frequency. The desired frequency refers to the fundamental frequency (fO or first partial) of the drum and-partials or overtones. The second partial (fl or first overtone) is the frequency range used for tuning the perimeter of the drum. One or more 'higher order' overtones may be used for tuning purposes, or certain preferred intervals between the fundamental and its overtones may be used as desired frequencies for tuning, so as to obtain a desired musical effect, sound timbre, a sustain or a decay time. The number of sensors on the drumhead may be chosen to correspond to the number of tensioning lugs on the shell, but any combination of sensors and tensioning lugs is included in this invention.

[0055] The tuner may comprise a display for communicating information to the user. The display may comprise a graphic depiction of a drumhead and the tensioning lugs, together with graphic instructions for adjusting the tensioning lugs, for example a semi-circular arrow, either pointing clockwise indicating a desired tightening of the tensioning lug, or pointing counter-clockwise for a desired loosening. The tuner may also present a graphic display of the tuning signal as a time-domain variable or a frequency-domain variable, for example in the form of a sonogram or spectrogram. The display may also indicate intervals between drums or heads, expressed in frequency, notes or interval naming.

[0056] The acquisition circuit may be any acquisition circuit known in the art. Particularly preferred examples of acquisition circuits for resistive sensors are the Wheatstone Bridge and the Anderson Loop. The Anderson Loop is particularly preferred because of its insensitivity to any differences in resistance of the leads. [0057] The signal acquisition circuits produce analog signals, which after conditioning may be converted to corresponding digital signals using an analog/digital converter. The digitized signals may be subjected to multiplexing to allow serial processing. The device suitably comprises a memory for buffering and other memory functions.

[0058] As will be explained in more detail below, for certain functions of the device, in particular triggering and sound generation, it is important that the latency of the device be kept as short as possible. For sound generation the latency is preferably 12 ms (milliseconds) or less, more preferably 5 ms or less. It will be understood that the type and size of the memory may have an impact on the latency. A Static Random Access Memory (SRAM) is preferred. [0059] The device further comprises one or more Programmable Logic Devices (PLDs). In principle all or part of the signal processing can be carried out by a suitably programmed general purpose computer, such as a PC or a Mac, a tablet, a smartphone, and so forth. For this purpose the device may convert the digitized signals to an industry standard format for wired or wireless data communication, such as USB 2.0 or USB 3.0, MIDI, Thunderbolt, Firewire, WiFi, Bluetooth, and the like. The general purpose computer, running dedicated software, then processes the signals, and may return the processed signals, or a desired output associated with the processed signals (such as a MIDI or other type of sound file) to the device. This is referred to as "off-board" computing. It has been found that off-board computing may undesirably add to the latency, and is not preferred for applications, such as sound generation, in which latency is important. It will be recognized that latency is not a primary concern in applications such as tuning.

[0060] Examples of suitable PLDs include Digital Signal Processors (DSPs); Discrete Wavelet Transformers (DWTs) and Field Programmable Gate Arrays (FPGAs). The choice of PLD and the appropriate programming of the logic device are governed to an extent by the need to keep the device latency within acceptable limits.

[0061] The PLD or PLDs produce digital signals that can be adapted to serve as inputs to digital drum peripherals, as exemplified by drum tuners and MIDI players. For the purpose of compatibility the device may be provided with an outlet or outlets for industry standard- compatible digital signals. Examples of suitable industry standards include MIDI, USB 2.0, USB 3.0, and the like. Wireless formats may also be used, including but not limited to WiFi, Thunderbolt, Firewire, Zigbee, Bluetooth, and the like. The format may be updated to adjust to new generations of such standards.

[0062] In a particularly useful embodiment the device converts the acquired signals to signals that can be used as input signals to commercially available drum brains. The input signal to the drum brain may be used in a variety of ways, for example to cause the drum brain to output a digital MIDI signal, or to activate a sound playback function of the drum brain or a hit detection triggering function of the drum brain. Manufacturers of drum brains include Roland, Yamaha, Alesis, Kat, Medeli, and the like. This feature offers drummers an opportunity to enjoy the benefits of the sensors embedded in a percussion membrane with equipment they may already own or may readily acquire.

[0063] An impact of the percussion membrane (for example, a beat with a drumstick) produces a sound that is caused by a vibration of the percussion membrane, and that is characterized by four main parameters: (i) the location of the impact; (ii) the time of the impact; the amplitude of the vibration resulting from the impact; (iv) the frequency of the vibration resulting from the impact; and (v) the spectral content distribution of the vibration resulting from the impact. [0064] In addition to the four main parameters, the spectral content distribution can be used to determine an acoustic signature of the impact, which can be used as a means for recognizing the type of hit that caused the vibration. Observed within a typical timeframe, the acoustic signature of an impact type or a hit type consists of a defined set of characteristics, which comprise one or more of the following: a typical dynamic envelope; a typical spectral power distribution; a typical spectral flux in one or more spectral bands; a typical rhythmic pattern or sequence; a typical excitation of at least one specific impact location; a typical amplitude; a typical signal arrival time difference; or a combination thereof.

[0065] Even when the sensor signals of two different hit types are of equal average amplitude in the time domain, it is still be possible to distinguish them based upon their typical acoustic signature, by detecting their typical spectral content distribution in the frequency domain. A combination of time domain and frequency domain information allows for further refinement of the acoustic signature. For example, when a drum is struck on the rim or counter hoop, the spectral content of the sensors is different than when the same drum is struck in the center of its membrane. The sensor signal typically contains more energy in the frequency bands above the fundamental frequency of the membrane in case of a hit on the rim or the counter hoop. However when the hit took place in the center of the membrane, the various sensor signals typically contains more energy in the spectral band around the fundamental frequency of the membrane. Furthermore, depending on the individual sensors' positions with respect to the impact location, their respective amplitudes and signal arrival time differences contribute to the acoustic signature of each of two different hits. For example, when the sensors are equidistantly placed on a circle near the edge of the percussion membrane of a drum, a stroke in its center typically displays lower relative differences between the amplitudes and arrival times of the various sensor signals than when the drum containing the membrane is hit on a location on its rim or counter hoop. In the latter case, the signals of the sensors will display a great variation in signal arrival times and amplitude as a consequence of their different distances to the impact location It will be clear to a person skilled in the art that an acoustic signature associated with a specific hit type can be of greater describing accuracy when combining characteristic of both the time and the frequency domain, in such a way it is possible to distinguish a hit on the counter hoop or rim of the drum from a hit on the outer edge of the membrane, nearby the impact location. [0066] For optimum determination of the impact location it is desirable to provide at least four sensors embedded in a percussion membrane in vibrational connection to the percussion membrane. The sensors are preferably equidistantly placed on a circle near the edge of the percussion membrane. Depending on the type of drum, the location of the sensors on the percussion membrane can be varied in order to obtain the best performance of the envisioned application functionality. In case of a percussion membrane that is a surface in a practice pad, the sensors may be positioned closer to the center of the membrane for example. Similarly when the type of drum is an acoustic cymbal, placement of one or more sensors near the bell of the cymbal and near the outer edge of the cymbal may be preferable. [0067] The location of the impact is important for determining the type of sound that the impact produces, A drum beat near the center produces a deeper, booming sound wherein the fundamental frequency of the head is pronounced. The same drum when beat near the edge produces a crisper, higher pitched sound with more pronounced overtones. The ability to determine the location of the impact allows for production of a sound having characteristics that correspond to the location of the impact.

[0068] In principle the location can be determined with the signal of one sensor as the position of the sensor in relation to the drumhead's center is known. An impact near the center of the drumhead results in a wave with a greater pulse width than an impact near the edge of the drumhead. The pulse width can be determined, for example, by the first wave half time, as explained in US Patent No. 6,271,458, the disclosures of which are incorporated herein by reference. The pulse width can be calibrated during tuning or, for example, at the start of each playing session, by striking the drumhead a number of times in the center and at a predetermined location near the edge.

[0069] The pulse width method determines the distance of the impact location from the center of the drumhead. That is, the result indicates that the impact was somewhere on a circle with a given radius, but not where on the circle the impact was. For many purposes this is sufficient information, because a drumhead is circle-symmetric.

[0070] A more accurate calculation of the impact location can be obtained with the signals of more than one sensor. The various sensors will detect a start of a vibration at the exact same time only if the impact was in the very center of the drumhead. An off-center impact will result in a time difference between the respective sensor signals. Various time-of- flight algorithms are available in the literature for determining the impact location from the time differences between the respective sensor signals.

[0071] A reasonable approximation may be made by drawing a straight line between the sensor with the earliest signal and the sensor with the latest signal. If the speed of wave propagation in the drumhead is known, the location on the connecting line can be determined. It's not precise, because the actual location may not be on the connecting line. But the approximation is a reasonable one, and this method of positioning saves computing time.

[0072] Another reasonable approximation may be made by implementing case based models wherein for example different amplitudes of a multitude of sensors can be compared to decide upon a possible area related to an impact position. Also the frequency distribution in the frequency domain or the pulse width in the time domain can be taken into account for a multitude of sensors or a sum thereof.

[0073] The signals of three sensors can be used for positioning using standard triangulation. However, the time of the impact is not known, so that a fictitious impact time must be used for this method.

[0074] Use of the signals of at least four sensors allows for an accurate determination of both the location of the impact and its time. The time does not need to be determined in an absolute sense. It is, however, important to assign an impact time to a signal in order to discriminate between signals resulting from different impacts that are close in time. [0075] Alternatively the signals of two or more sensors can be used for positioning by using case-based approaches that take signal amplitude and/ or time difference of arrival into account. This approach may be suited for defining one or more concentric zones and/ or one or more radial impact zones. For example, on a circular percussion membrane with multiple sensors equidistantly placed on a circle with a given radius near the outer edge of said percussion membrane, two concentric zones may be defined by setting a time difference of arrival threshold that defines the boundary between a central circular area and a surrounding angular shaped area. When an impact takes place on the abovementioned percussion membrane, the relative time difference of arrival of the resulting vibration at the various sensors provides an indication of the position of impact. By comparing the largest detected time difference of arrival between the respective sensor signals with a time difference threshold, it may be case-base determined whether the impact took place in the outer angular area or in the central circular area of the percussion membrane. A preferred embodiment of case-based positioning uses a percussion membrane with three or more embedded sensors.

[0076] If the largest detected time difference of arrival between the respective sensor signals is below a predetermined time difference threshold, then it may be case-base decided that the impact was inside the central circular area. If the largest detected time difference of arrival between the respective sensor signals is above a predetermined time difference threshold, then it may be case-base decided the impact took place in the surrounding angular shaped area. Similarly by defining multiple time difference of arrival thresholds, multiple concentric zones may be defined.

[0077] By comparing the relative amplitudes of the various sensor signals after impact, it may be decided which of the various sensors is located the closest to location where the impact on the percussion membrane took place. The amplitude of a sensor signal is typically directly proportional to the distance between the sensor location and the impact location on the percussion membrane. When a radial area is attributed to one or more sensors, the percussion membrane may be divided in one or more radial areas. When combining amplitude-based and time difference of arrival-based sensor signal observations, impact sectors may be identified that consist of the overlap of concentric and radial zones.

[0078] A particular benefit of having various sensors around the perimeter of a membrane is the possibility of accurate impact velocity detection. Analyzing from multiple sensors allows for accurate impact velocity detection, when all amplitudes of the various sensor signals are taken into account to determine the velocity of a hit. A problem that is often encountered with today's sensors used in electronic or hybrid drums, is that the data of a single sensor signal typically do not provide a faithful indication of the impact velocity of a hit, because the perceived velocity of an impact is related to the distance between the impact location and the sensor location. Having multiple sensors will solve this problem.

Furthermore in a drum where multiple sensors are embedded in a single membrane, component cost and assembly cost is significantly reduced and structural robustness enhanced, compared to a drum wherein installing and wiring multiple piezo transducers to be in contact with a membrane is required. [0079] Conveniently the location of the impact is associated with a zone on the surface of the drumhead. In principle each mathematical point on the drumhead's surface can be considered a zone. Any such zone can be MIDI mapped and can be triggered to output a sound associated with it. It is, however, more practical to define a number of zones in line with the number of physical input channels available on the drum brain with which the device will be used. For example, if an impact is determined to have taken place in zone "1", the corresponding signal is given a label "1", and is sent (after processing and digital/analog conversion) to input channel "1" of the drum brain. The drum brain can be programmed to synthesize a sound corresponding to the sound of an acoustic drumhead when hit in zone 1 , or to play a MIDI sound mapped to this zone.

[0080] It is possible to define zones that produce special effects. For example, a zone can be defined to produce the sound of a bass drum, a snare drum or a cymbal, or even an organ or a flute. It is also possible to assign specific software functions to individual impact zones. For example, a zone can be defined for activating and/or deactivating a metronome function, for controlling a recording function, for controlling the playback of a loop or song, for controlling software parameters like click-track tempo, for controlling dedicated MIDI sounds, for controlling practice software, for controlling lights, or even for controlling the device, or switching between settings and operational modes of the device.

[0081] The signal received from the analog/digital converter may be analyzed for pitch (frequency) and loudness (amplitude). The processor may be programmed to generate an emulated piezo electric signal, be it in digital form at this stage. The emulated piezo signal may be generated in function of the location impact, and may be proportional to the impact velocity. The pitch and loudness parameters are used to generate an emulated piezo signal of appropriate duration, amplitude and frequency. The characteristics of the signal generated for input into a drum brain may be selected to match the input requirements of the drum brain. In appropriate cases the emulated piezo signal may comprise a block wave of a predetermined duration and amplitude, or it may have a saw tooth shape with an inclining or, preferably, declining slope, or it may have a sinusoid shape with an inclining or, preferably, declining amplitude and or frequency, and so forth. The emulated piezo signal may combine signals of different forms. The emulated piezo signal is converted to analog form, so it can be input to a drum brain. [0082] The device may produce an input signal for application software ("App") on a personal computing device, such as a smartphone, a tablet, a personal computer, and the like. The input signal for the App may be communicated via a suitable connector, such as a USB connector or an Apple Air connector, or wirelessly for example using a Bluetooth, Zigbee or WiFi protocol. The App may provide additional functionality, as well as provide internet connectivity to the device.

[0083] The App may provide tools to a user to enhance the user's playing pleasure. For example the App may contain study aids that help the user when practicing drum skills, such as a metronome, sound loops, education software, skill ranking, skill progression monitoring, and the like. The App may allow the user to participate in a user community, for example in drumming related games, drumming contests, and the like. The App may allow the user to upload sound tracks created by the user, so as to invite constructive criticism or to generate performance opportunities.

[0084] The App may provide the user with relevant information, such as upcoming concerts and events, newly released music of a genre of interest to the user, reminders for drumhead replacement, newly launched equipment and peripherals, and the like.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS/EXAMPLES

[0085] The following is a description of certain embodiments of the invention, given by way of example only.

[0086] Figure 1A shows a perspective view of drumhead 10; Figure IB shows a top view. Drumhead 10 is provided with annular ring 12, which can be used for attaching drumhead 10 to a drum shell, in known fashion. Drumhead 10 is provided with eight capacitive strain sensors 11 A through 11H, placed at equal distances on a circle near the circumference of drumhead 10. Leads 13 printed onto drumhead 10 serve to conduct signals from the strain sensors 11 to tab 14. Tab 14 can be electrically connected to a connector (not shown).

[0087] Figure 2A shows a perspective view of drumhead 20; Figure 2B shows a top view. Drumhead 20 is provided with annular ring 22, which can be used for attaching drumhead 20 to a drum shell, in known fashion. Drumhead 20 is provided with eight resistive strain sensors 21 A through 21H, placed at equal distances on a circle near the circumference of drumhead 20. Leads 23 printed onto drumhead 20 serve to conduct signals from the strain sensors 21 to tab 24. Tab 24 can be electrically connected to a connector (not shown).

[0088] Figure 3A is a schematic representation of an inner portion of drumhead 30. Sensors SI, S2, S3 and S4 are resistive sensors, randomly located on circle CS. Shown on drumhead 30 are exemplary impact locations 31 through 39. Impact location 31 is the center of drumhead 30, as well as of circle CS. Each location can be defined by its distance r from the center, and its angle Θ from the horizontal.

[0089] Figure 3B shows signals acquired from sensor S4 by means of a Wheatstone Bridge circuit using a 5 Volts acquisition voltage. Graphs A through E represent five different impacts of equal amplitude. The X-axis shows the time in seconds, t=0 being the time of time of the impact. Graph A represents an impact at location 33, nearest sensor S4. Graph represents an impact at location 32; Graph C at location 31; Graph D at location 37, and Graph E at location 38. From A to E the graphs represent increasing impact distances from sensor S4. [0090] As can be seen from Figure 3B, the travel times of the wave fronts to sensor S4 from the various impact locations is on the order of several milliseconds, which is ample to serve as a basis for using signals of this type for determining the impact location with reasonable accuracy. The graphs also show that the signals acquired by sensor S4 are information rich. [0091] Figure 4 is a schematic representation of an exemplary configuration of a device according to the invention.

[0092] Drum 40 has a batter head 40 A and a resonant head 40B. Each of heads 40 A and 40B is provided with six resistive sensors. The sensors are operationally connected to a signal acquisition circuit 42. Drumstick 43 causes an impact on batter head 40A, causing batter head 40 A to vibrate. Resonant head 40B vibrates in resonance to batter head 40 A. In cooperation with acquisition module 42, each of the sensors produces a signal proportional to the stretch of heads 40A and 40B at the respective locations of the sensors. The signals are schematically depicted in boxes 41 A and 4 IB.

[0093] The acquisition module may be placed in a protective housing on the side of drum 40, as shown at 49. Housing 49 may further contain a battery for powering the acquisition module. The acquisition module contains a number of acquisition circuits, for example one circuit for each sensor. Conditioning circuits may be integrated in the acquisition module. Conditioned signals acquired by acquisition circuit 42 are passed on to analog/digital converter 44. Signals acquired by acquisition circuit 42 can also be passed directly to Modeling Module 47 as an analog signal for further processing or even direct output.

[0094] The acquisition module may alternatively be attached to, or integrated with the drum's structure, or be integrated with a structural component of the drum. For example the acquisition module may be integrated in a structural component of a drum tensioning hoop, a drum lug, a snare wire strainer, a drum bracket used for mounting drums to stands or racks, a drum support, or mount, a suspension system, a rim, in the enclosure of a pad, and the like.

[0095] Digitized signals from analog/digital converter 44 can be passed on to one or more of a number of signal processing modules, exemplified in Figure 4 by Tuning Module 45, Triggering Module 46, and Modeling Module 47.

[0096] In Tuning Module 45, signal pre-processing takes place in pre-processing sub- module 45 A. For example, the user may enter a selection for tuning resonant head 40B, which causes sub-module 45A to block signals from batter head 40A so as to not unduly burden signal processing sub-module 45B.

[0097] Sub-module 45B processes the signals from the various sensors based on one or more parameters that are relevant for tuning. For example, a coarse initial tuning may involve analysis of the pulse width of each signal. Once the coarse tuning is completed, sub-module 45 B may switch to analyzing the first overtone (second partial) reported by each sensor as a means for fine tuning the drumhead being tuned. In an alternate embodiment the coarse tuning step is skipped.

[0098] Signal output sub-module 45C produces an output signal. This may be in the form of an industry standard compatible signal, such as MIDI, USB 2.0 or USB 3.0, WiFi,

Thunderbolt, Firewire, Bluetooth, or the like, which may be received by a general purpose computer or by a smart phone. The computer or smartphone may contain dedicated software, for example an app, some form of program, widget or a plug-in, that converts the output signal of module 45 to a form that carries useful information for the user, for example an audible tone, alphanumerical frequency and note information, an interval naming in relation to one or more loaded presets or stored, previously received datasets, an ADSR envelope, a 3D spectrogram, a display of a wave form, or a schematic depiction of a drumhead showing, for example, which lugs need tightening and/or which lugs need loosening.

[0099] The output signal from sub-module 45C may be in a form adapted to the input requirements of a dedicated tuning device.

[00100] Triggering Module 46 produces an output signal based on one or more of the location and timing of an impact, and amplitude, the type of stroke, hit or impact (flam, roll, rim click, rim shot, single stroke etc...) and/or frequency spectrum of the resulting vibration.

[00101] In one embodiment, drumhead 40A is divided in zones. Module 46 determines the number, the location and the shape and area of the zones on a drumhead and determines the zone in which an impact took place. Each zone can be associated with a sound or a functionality of a specific type. For example, a first zone may be associated with the sound of a snare drum; a second zone with the sound of a torn; a third zone with the sound of a bass drum; a fourth zone with the sound of a cymbal; a fifth zone with a click-track functionality, etc. Triggering Module 46 determines the time of impact and the zone in which the impact took place, and outputs a signal instructing a drum brain a general purpose computing device with dedicated software, or a synthesizer to produce the sound or execute the functionality associated with that zone. The Triggering Module 46 may determine the loudness of the sound based on an amplitude of the signal, and use this information to instruct the drum brain or synthesizer to produce a sound having a specific loudness, amplitude, MIDI velocity and the like.

[00102] In an alternate embodiment of Triggering Module 46, or in an alternate mode of operation of Triggering Module 46, the output signal emulates an output signal of a piezo electric trigger, so that the output signal can be processed by a drum brain adapted for piezo electric drum triggers. In a basic form Triggering Module may identify the strongest of the sensor signals (for example, the signal from the sensor nearest the point of impact). This signal is then analyzed for attributes such as amplitude, frequency and decay, which parameters are then used for emulating a piezo electric signal of corresponding amplitude frequency and decay characteristics. [00103] In a more elaborate form Triggering Module 46 may make fuller use of the richness of the data provided by the sensors. First the signals from all sensors are multiplexed in preprocessing sub-module 46A. Signal processing sub-module 46B then determines the location of the impact from the timing differences between the signals from the sensors present on batter head 40A. It further analyzes the signals for amplitude, timing, and type of impact. These factors can be used to determine the input channel of the drum brain to which the signal is output, the loudness of the sound to be synthesized. The Triggering Module 46 may determine the type of hit based on the acoustic signature of the signals from the sensors present on batter head 40A, optionally combined with the acoustic signature of the signals from the sensors present on resonant head 40B, and use this information to instruct the drum brain or synthesizer to produce a sound that corresponds to this specific type of hit (flam, roll, rim click, rim shot, single stroke etc...), or to execute a functionality associated with it.(E.G. a flam in a certain zone activates metronome etc...).

[00104] In a similar manner an acoustic signature of hits can be compared to and matched with previously determined hits of a certain type, in order to decide upon a selection of a hit type that corresponds to a the vibration characteristics of a received hit. This allows defining and recognizing the acoustic signature of different instruments on a wide range of drums and percussion membranes.

[00105] In yet another embodiment Triggering Module 46 generates an output signal that is suitable for an audio amplifier and/or a speaker or headphones. The output signal can be an audio signal, like a MIDI sound or a synthesized sound. The output signal may be a composed audio signal in relation to the acoustic signature of a vibration of the percussion membrane. To this end Triggering Module 46 analyzes the signal to determine the

fundamental frequency of the vibration, and the presence and relative loudness of any overtones. In this determination it may use data from a preceding tuning of the same drum, which data may be stored in memory. Based on a determination of the fundamental frequency and overtones, the Triggering Module 46 creates a number of sine waves, which are combined to form an emulated sound wave. The location of the impact can be used to modify the sound wave corresponding to the distance of the impact from the center of drumhead 40A, for example. [00106] Modeling Module 47 may receive analog signals directly from acquisition module 42, or receive converted digital signals from analog/digital converter 44. Modeling Module 47 comprises dedicated signal conditioning. Modeling Module 47 analyzes the incoming signals as proper sound waves that may be contaminated with noise. Module 47 cleans up the signals by filtering out the noise; it may also (partially) filter out non-harmonic overtones. The resulting output signal of Module 47 is a faithful rendition of the actual sound of the drum, and can be sent to a PA system or recorder as if it were a microphone output. It will be understood that Modeling Module 47 may be programmed to manipulate the sound by emphasizing the fundamental frequency, adding reverb or echo, and the like. It will be understood that Modeling Module 47 may also be equipped as an amplification, equalizing and mixing module to manipulate the sound by amplification, emphasizing frequency bands, filtering frequency bands, adding reverb or echo, mixing, panning and blending the input and output channels and the like.

[00107] Modeling Module 47 may also dynamically shape an output signal to one or more spectral envelopes in the frequency domain, possibly in combination with an amplitude envelope in the time domain. These envelopes may be dynamically acquired by analyzing one or more sensor signals over time, for example by analyzing a continuously moving or hopping sample window. In a preferred embodiment variations in spectral content distribution in the frequency domain and variations in amplitude in the time domain may be used to create one or more dynamic envelopes. Such envelopes may represent spectral content transients in the full frequency spectrum, or of one or more frequency bands of interests, and may be combined with an amplitude envelope in the time domain

proportionally related to the amplitude of the signal generated by at least one of the various sensors embedded in the percussion membrane. [00108] The creation of such envelopes allows to dynamically describe the acoustic behavior of the percussion membrane in terms of the power distribution of the spectral content of interest and the dynamic state of the percussion membrane over time. Envelopes describing impacts on the percussion membrane and their acoustic signatures can in such a way be used to shape an output signal in close to real-time in order to generate an output that is spectrally rich, offering endless variation possibilities, while faithfully following the acoustic behavior of the percussion membrane. This approach permits a faithful translation of a musician's playing style or the sound quality of the instrument into an output signal that is not limited by MIDI expression qualities.

[00109] Modules 45, 46 and 47 may be put together in one housing as a multi-functional unit, which may also contain analog/digital converter, as indicated by dotted line 48. Such a multi-functional unit may be adapted to process signals acquired from a plurality of drums, for example all drums of a drum set. The multifunctional unit may be powered with network power, and may be set up to provide acquisition module 42 with its power needs, so that acquisition module 42 is independent from battery power.

[00110] In an alternate embodiment, modules 45, 46 and 47 may be separate pieces of equipment. Conversely, analog/digital converter 44 may be integrated with acquisition module 42. One or more of the tasks of modules 45, 46 and 47 may be carried out off-board, for example by a suitably programmed general purpose computer or smartphone.

[00111] Figure 5 shows an alternate embodiment of the device of the invention. Device 50 comprises a signal acquisition module 51, a signal throughput module 52A, and a piezo emulator 52b.

[00112] Signal acquisition module 51 comprises signal acquisition circuits 53 and analog/digital converter 54. In this specific embodiment acquisition module 51 further comprises signal acquisition unit 55 for acquiring signals from a rim mounted piezo trigger. A rim mounted piezo element serves to detect whether the batter has hit the rim of the drumhead, so that an appropriate sound associated with a rim hit may be generated. A rim hit may also be detected by triggering Module 46 of Figure 4, based on the acoustic signature of the signals from the sensors present on batter head 40A optionally combined with the acoustic signature of the signals from the sensors present on resonant head 40B. In case of a pad the acoustic signature of the detected hit will be compared with previously stored signatures to define hit type or impact area / location.

[00113] Signal throughput module 52A comprises SRAM 57 and FPGA 56. SRAM 57 serves to buffer incoming signals, and is available for other memory functions as well. FPGA 56 contains embedded software for processing signals for tuning, triggering and/or modeling, as described with reference to Figure 4. Signal converter 58 converts signals output by FPGA 56 to an industry standard-compliant signal, suitable for wired or wireless data communication, such as USB 2.0; USB 3.0; Firewire, Thunderbolt , MIDI, WiFi, Bluetooth or the like. This is indicated by USB icon 58 A.

[00114] The industry standard-compliant signal can be output via output line 58B. The signal may comprise tuning data, such as the Fo and the Fi for each sensor, and/or the target tone offset for each sensor. Instead of or in addition to tuning data the signal may comprise triggering data, for example MIDI timing and impact; MIDI channel and impact; an MIDI velocity and impact. In appropriate cases the output from output line 58B can be an analog signal.

[00115] Piezo emulator 52B obtains a digital form piezo emulation signal from FPGA 56, and converts it to an analog signal with digital/analog converter 59. The analog piezo emulated signal is output to one of channels A, B, C, D and E of a brain drum (not shown). The channel label is provided by FPGA 56 and is based on a determination of the location of the impact carried out by FPGA 56.

[00116] Figure 6 is a schematic representation of a device comprising an output for direct amplification.

[00117] The system shown in Figure 6 comprises a percussion membrane 61 having a number of embedded sensors (not shown). Percussion membrane 61 comprises a connector tail 61C, which contains the contacts for the sensors embedded in percussion membrane 61. Tail 61C is connected to conditioning circuit 62 via connector 62A, which may be made of a conductive elastomer like a Zebra® connector or a ZIF FCC connector, for example.

Conditioning circuit 62 is connected to sound amplifier 63 via connectors 62B and 63 A. Connectors 62B and 63A may be XLR connectors, for example. Amplifier 63 may be any amplifier suitable for amplifying sound signals, such as a guitar amplifier, a mixer table or a PA system. [00118] Conditioning circuit 62 acquires an analog signal from percussion membrane 61 via lead 61 A. After signal conditioning the analog signal is passed on to amplifier 63 by lead 62C.

[00119] The system further comprises a signal processing device 64, which comprises an analog-to-digital converter and digital signal processing circuits. Device 64 receives a conditioned analog signal from conditioning circuit 62 via 62D. [00120] The system further comprises a power supply 64 A, for example a rechargeable battery, such as a Lithium-Polymer battery. Power supply 64A is shown as being integrated with device 64. It will be understood that power supply 64 A may instead be integrated with conditioning circuit 62, or may be separate from both device 64 and conditioning circuit 62. [00121] Device 64 produces a digital signal that serves as an input signal for peripheral device 65. Peripheral device 65 can be any device suitable for receiving a digital signal from a drum interface, such as a drum brain, a MIDI player, a computer, and the like, as described in more detail hereinabove. Device 64 may communicate with peripherally device 65 wirelessly via 64B and 65B, or through wired communication via 64C and 65C. Wireless connectors 64B and 65B may communicate via a wireless standard, such as Bluetooth, or via another wireless standard as described in more detail hereinabove. Wired connectors 64C and 65C may be USB 2.0 connectors or some other type of wired connectors, as described in more detail hereinabove.

[00122] Power supply 64A may receive power from amplifier 63 via leads 63B, or from peripheral device 65 via lead 65D. Power supply 64A may provide power to device 64 and conditioning circuit 62. Conditioning circuit 62 may provide power to percussion membrane 61 via lead 61B.

[00123] Figure 7 is a schematic representation of a device interacting with an App running on a general purpose computer or a smart purpose computer like a smart phone or tablet.. [00124] The system of Figure 7 comprises a percussion membrane 71, which comprises embedded sensors 7 IB and 71C. Depicted sensors 7 IB and 71C represent any desired number of embedded sensors. A user may provide input into percussion membrane 71, as represented by arrow 71 A. The user's input 71 A may comprise any action causing percussion membrane 71 to vibrate, such as a hit with a drum stick, a mallet, a brush, a hand palm, a fist, one or more fingers, and the like. The user's input 71 A may be of a type that does not necessarily produce sound, such as a tightening or loosening of lug nuts or the operation of a foot pedal.

[00125] Percussion membrane 71 is connected to device 72, which may be a device as shown in Figure 4 or 5 and described in the text accompanying Figures 4 and 5. A user may provide input to device 72, as shown by arrow 72A. User input may be any input relating to the operation of device 72, for example selection of an operation mode of device 72, such as triggering, tuning, or direct amplification. Device 72 is connected to controller 73, which controls the operation of device 72. Generally, and preferably, controller 73 is integrated with device 72. A user may provide input to controller 73 at 73A. A user's input to controller 73 may comprise parameters relating to the electronic circuitry of device 72, such as

amplification, filtering, shielding, and the like. Controller 73A may also comprise external controllers such as a foot pedal, a keyboard, and the like. Controller 73 may provide input to device 72 via 73B, and/or to App74 via 73D.

[00126] Output 72B of device 72 may be communicated to any suitable device, such as a drum brain, a MIDI player, a drum tuner, a PA system, etc., as described in more detail hereinabove. A specific feature of the system of Figure 7 is output 72C to a general purpose computing device comprising application software (App) 74. The general purpose computing device (not shown) may be a PC, a Mac, a smartphone, a tablet, or the like. App 74 may contain any type of software related to drumming, including but not limited to tuning, practicing, education, amplification, sound effect generation, emulation of drumming, sheet music reading and/or writing, music composing, tempo and playing accuracy tracking, recording of drumming sessions, skill rating, skill assessment, progress assessment, loop generation, and the like.

[00127] A user may provide input to App 74 at 74 A. Such input may relate to the operation of App 74, such as selecting a functionality of App 74 to run or not run, display preferences, and the like.

[00128] App 74 provides output to the user at 74B. Such output may be in the form of a display presented on a screen of the general purpose computer, and/or a sound, and/or a vibration, and/or comments on a user's skills, and the like. [00129] The functionality of App 74 may be expanded with expansion module 75.

Expansion module 75 may run as a separate module on the general purpose computer, or it may be integrated with App 74. For example, App 74 may be made available to the user at no cost or at a nominal price. Expansion module 75, offering additional functionalities and/or more sophisticated versions of the functionalities of App 74, may be offered to the user as an upgrade of App 74, at a higher price than the price charged for App 74. Expansion module 75 comprises functionalities 75 A, 75B, 75C, 75D, etc. Expansion module 75 interacts with App 74 as shown schematically by arrows 75AA, 75BB and 75CC.

[00130] App 74 may be connected to a user community 76, for example via the Internet. The user of App 74 participates in user community 76 via user account 76A. Within the user community the user with account 76A may interact with other users 76B and 76C via

(temporary) connections 76BB and 76CC, in a manner known from social networking apps. User account 76A may allow the user of App 74 to upload information related to the user's status, skill ranking, statistics, and/or publicity, event announcements, advertisements, and the like, or educational materials developed by the user. User account 76A may further allow the user of App74 to participate in games, contests, competitive rankings, content sharing, chat rooms, education, and the like.

[00131] User account 76 A may further provide contact with relevant parties that are not part of user community 76, as shown by double arrow 76D. Such relevant parties may include suppliers of a variety of products, such as drum or other musical equipment, software, sound libraries, plug-ins, and the like, other user groups, event organizers, concert organizers, content providers, and the like.

[00132] Thus, the invention has been described by reference to certain embodiments discussed above. It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art. For example, the device may be modified by incorporating self-learning software so that the device becomes better at interpreting acoustic signatures of sensor signals as it is used with a specific drum or drum set for a prolonged period of time. The device may be programmed to track the playing time of a drumhead, the number of impacts over time, the absorbed total impact velocity over time, etc., and, possibly in combination with an analysis of the quality of the spectral content of the vibration of a drumhead, notify the user when the drumhead is due for replacement. The device may be connected to the Internet or the cloud, wired or wirelessly, for example via a WiFi connection, to allow expansions, maintenance or periodic updates of its embedded software or firmware. The device may contain a sound library, which may be expanded with library items from the Internet and the user's own recordings. The device can be adapted to process signals from any type of drumhead sensor. [00133] Many modifications in addition to those described above may be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A device for acquiring signals from one or more sensors embedded in a percussion membrane, said membrane defining an x-y plane, and converting said signals to input signals for a drum peripheral instrument, said device comprising:

a. one or more signal acquisition circuits for acquiring analog signals comprising signals caused by strain within the x-y plane of the percussion membrane from the one or more sensors;

b. one or more conditioning circuits for conditioning the analog signals acquired in the one or more acquisition circuits.;

c. means for inputting the conditioned signal obtained in b. into a sound amplification system or an analog-to-digital converter.

2. The device of claim 1 further comprising:

d. an analog-to-digital converter for converting conditioned analog signals from the one or more conditioning circuits;

e. a processor for processing the digital signals produced in d.

3. The device of claim 2 wherein the processing of the digital signals in e. comprises converting the digital signals to a digital form of drum-brain compatible signals.

4. The device of claim 3 wherein the drum peripheral instrument is a drum-brain, and the device comprises a digital-to-analog converter.

5. The device of any one of the preceding claims wherein the drum peripheral

instrument is a drum tuner.

6. The device of any one of the preceding claims wherein the drum peripheral

instrument is a computing device running applications software.

7. The device of claim 6 wherein the applications software connects a user of the device to the Internet or the cloud.

8. The device of any one of the preceding claims wherein the one or more signal acquisition circuits comprise Wheatstone Bridge circuits and/or Anderson Loop circuits, preferably Anderson Loop circuits.

9. The device of any one of the preceding claims wherein the processor comprises one or more Programmable Logic Devices (PLDs).

10. The device of any one of the preceding claims producing an industry- standard

compatible digital signal.

11. The device of any one of the preceding claims wherein signals acquired from the one or more signal acquisition circuits are split into an x-y component and a z-component.

12. The device of claim 11 wherein the x-y component is used in tuning or triggering.

13. The device of any one of the preceding claims for acquiring signals from two or more, preferably three or more, more preferably four or more sensors embedded in the percussion membrane.

14. The device of any one of the preceding claims wherein the one or more sensors

comprise a pattern of conductive material coated onto the percussion membrane or onto a surface vibrationally connected to the percussion membrane.

15. The device of any one of the preceding claims adapted to analyze sensor signals

resulting from an impact applied to the percussion membrane to determine one or more of (i) the location of the impact on the percussion membrane; (ii) the time of the impact; (iii) the amplitude of a vibration resulting from the impact; (iv) the frequency of the vibration resulting from the impact; and (v) the spectral content distribution of the vibration resulting from the impact.