JPH0522740Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a speaker device used in an electronic muffling device for muffling noise from a blower of an air conditioner.

[Prior Art] In an air conditioner for a hall, etc., the rotating sound of the blower, wind noise, resonance sound of the duct, etc. are transmitted through the ventilation ducts arranged in a congested manner inside the building, and are transmitted through the ventilation openings or ducts to the guest rooms, etc. The noise level leaking to the outside is relatively high.

To solve this problem, as shown in Fig. 7, a microphone 2 installed inside the duct 1 picks up the noise generated and transmitted within the duct 1, and the output is passed through a digital filter 3 to reverse the noise input characteristics. By amplifying the output with an amplifier 4 and driving a speaker 5 housed in a speaker box 6 installed in an opening 11 bored in the wall of the duct 1, a speaker opening is arranged in the duct 1. , the noise level in duct 1 (approx.
Attempts are being made to lower the level (which can reach 100 dB in some cases).

[Problems to be solved by the invention] However, in the conventional speaker device described above, when the output of the blower 10 increases or the wind pressure increases, in some cases, the 55
Static pressure of mAq (55Kg/m ² ) is applied as a pulsating flow, so in the above-mentioned speaker device, the diaphragm 12 vibrates with a large amplitude, and the voice coil jumps out of the magnetic gap and operates. There was a problem that caused an inability to operate.

[Means to solve the problem] This idea uses a microphone placed in the duct,
A digital filter that receives the output of the microphone as an input, an amplifier that receives the output of the digital filter as an input, and a speaker that receives the output of the amplifier as an input, the speaker being arranged so that its radiation direction faces into the duct. and a means for communicating the space before and after the diaphragm of the speaker.

[Function] According to the configuration of this invention, the space before and after the diaphragm is communicated, and the static pressure in the duct and the static pressure in the space behind the speaker diaphragm are balanced, so that the size of the diaphragm due to the static pressure in the duct is reduced. Amplitude motion can be prevented.

[Example] This idea will be explained below with reference to examples.

In FIG. 1 (common parts with the conventional example are given the same numbers), 10 is a blower which blows air (mainly purified air) to various places through the duct 1. A pickup microphone 2 is installed in a duct 1 2 to 3 m from the blower, and the output of the microphone 2 is passed through a digital filter 3 with its phase reversed and input to an amplifier 4.

A speaker box 6 is attached to an opening 11 formed in the wall of the duct 1.

A speaker 5 having a diameter of 30 cm is attached to the speaker mounting plate 8 of the speaker box 6, and a small hole 9 of about 5 mm is bored in the speaker mounting plate 8.

Then, the speaker box 6 is connected to the duct opening 1.
1, the small hole 9 communicates between the duct 1 and the space within the speaker box 6.

Further, the diameter of the sound emitting port 7 in front of the speaker diaphragm is sufficient as long as the static pressure of the duct 1 is transmitted, and in this embodiment, the diameter was 5 cm.

If the diameter of the sound emitting port becomes too large, the amplitude of the vibration system including the speaker diaphragm 12 due to changes in the dynamic pressure within the duct 1 will increase, which is not preferable.

It is also possible to adjust the acoustic impedance by arranging a resistance element such as a sound absorbing material in the sound emitting port and/or the small hole.

2 to 6 show other embodiments in which the speaker 5 is attached to the duct wall 11 or the speaker box mounting plate via a spacer to create a gap between the speaker frame and the duct wall 11 or the mounting plate. The structure is such that the space before and after the speaker diaphragm is communicated by forming an arcuate slit 32 in the speaker frame 31.
By forming a small hole 41 in the speaker diaphragm 12, the space before and after the diaphragm is communicated with each other when the speaker 5 is attached to the duct wall 11 or the mounting plate. This configuration allows the space before and after the diaphragm 12 to communicate with each other.

Further, the embodiment shown in FIG. 5 has a configuration in which the speaker box 6 space and the inside of the duct 1 are communicated through a duct 51, and by selecting the shape of the duct 51, an acoustic filter effect can be obtained.

FIG. 6 shows a speaker box 6 made of a material 61 having air permeability.
The internal space is connected to the inside of the duct 1 .

[Effect of the invention] As is clear from the above explanation, this invention has a means for communicating the space before and after the speaker diaphragm, so that the static pressure in the duct located in front of the diaphragm is reduced through the communication means. Introduced into the rear space of the diaphragm, the static pressure in front and behind the diaphragm is maintained at the same pressure, eliminating displacement of the vibration system and preventing the voice coil from jumping out of the magnetic gap even if the noise level increases. can.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of this invention, FIGS. 2 to 6 are sectional views of main parts of other embodiments, and FIG. 7 is a block diagram illustrating a conventional example. 1...Duct, 2...Microphone, 3...Digital filter, 4...Amplifier, 5...Speaker.

Claims (1)

[Scope of utility model registration request] A microphone arranged in a duct 1, a digital filter 3 which receives the output of the microphone 1 as an input, an amplifier 4 which receives the output of the digital filter 3 as an input, and a speaker 5 which receives the output of the amplifier 4 as an input. An electronic silencing speaker device, characterized in that the speaker is arranged such that its radiation direction faces inside the duct 1, and is provided with means for communicating the space before and after the diaphragm of the speaker 5.