JPH05158485A - Sound insulator - Google Patents

Abstract

PURPOSE:To sound-inslate noises ranging from low frequency to high frequency with small sized and compact configuration. CONSTITUTION:Noise detection signal is detected out of noise source by a noise detector 1, and a rectangular flat diaphagm 4a placed in front of an electro acoustic transducer 4 regenerates sound for cancelling noise. In addition, an acousto electric transducer 5 placed in front of the electro acousic transducer 4 detects error signal remaining without cancelled. Based on the error signal and the noise detection signal, a calculator 6 which performs convolution- calculation calculates, and the noise mainly in low frequency is insulated by controlling so that the coefficient of an adaptive filter 2 is updated for the error signal to be minimum based on the output. Further, a passive sound- inslating wall 22 placed at the back of the electro coustic transducer 4 insulates the noise mainly in high-frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soundproofing device having a soundproofing effect by silencing noise by an active noise control method in a noisy environment.

[0002]

2. Description of the Related Art In recent years, an active noise control method has been proposed in which a control sound is output from a speaker by using a digital signal processing technique to mute environmental noise at a listening position. Hereinafter, a soundproof device using a noise reduction effect by a conventional active noise control method will be described with reference to the drawings. FIG. 4 is a block diagram showing the structure of a soundproofing device when a passive soundproofing device using a conventional sound absorbing material and an active soundproofing device using a conventional active noise control method are used together. As shown in FIG. 4, as its components, 1 is a noise detector composed of a microphone or the like, 2 is an adaptive filter, 3 is a power amplifier, 4 is an electric / acoustic converter composed of a speaker, etc.,
Reference numeral 5 is an acoustic / electrical converter including a microphone, 6 is an arithmetic unit for performing a convolution operation, 7 is a multiplier, and 8
Is a preamplifier and 21 is a passive noise barrier.

With respect to the soundproofing device constructed as described above, the related operations of its constituent elements will be described below. The noise detection signal detected by the noise detector 1 is input to the adaptive filter 2. The noise detection signal adaptively controlled here is reproduced by the electric / acoustic converter 4 through the power amplifier 3. Then, the reproduced sound and the noise from the noise source interfere with each other, and the interference sound is detected by the acoustic / electrical converter 5. On the other hand, the noise detection signal is input to the arithmetic unit 6 which performs the convolution operation in which the characteristic of the control transfer characteristic C1 is set, is multiplied by the error detection signal by the multiplier 7, and controls the adaptive filter 2 by an algorithm such as the LMS method. Therefore, the adaptive filter 2 adaptively controls the noise detection signal so as to reduce the error detection signal. Further, at this time, in order to enhance the soundproof effect, a passive soundproof wall 21 is generally used together as another component.

[0004]

However, in the conventional structure as described above, in order to perform sound insulation up to a low frequency by the passive sound insulation wall 21, a material having a low transmissivity of low sound and a wavelength length are used. Area is needed. Such materials are now very expensive, heavy and
The scale of the device also increases. On the other hand, the active soundproofing device is effective at low frequencies, but has a problem that it is less effective at high frequencies where the wavelength is shortened. In view of the above problems, the present invention provides a soundproofing device capable of reliably soundproofing noise in a wide range of frequencies with a compact structure.

[0005]

In order to achieve the above object, a soundproofing device of the present invention comprises a noise detector for detecting noise from a noise source and an adaptive control of a noise detection signal detected by the noise detector. Adaptive filter, an electric / acoustic converter that reproduces an output from the adaptive filter, an error detector that detects an error between a sound from a noise source and a sound from the electric / acoustic converter, and an electric / acoustic An arithmetic unit that performs a convolution operation of the transfer characteristic from the converter to the error detector and the noise detection signal, and the output signal of this arithmetic unit and the error output from the error detector are multiplied, and the update signal of the coefficient of the adaptive filter And a multiplier for outputting
The acoustic transducer has a thin flat plate diaphragm and an error detector on the front surface and a soundproof material on the back surface.

[0006]

In the soundproofing device of the present invention having the above-described structure, a passive soundproofing wall which easily insulates high frequencies and an active soundproofing device which effectively silences low frequencies are integrated. That is, a sound for canceling noise is reproduced from the front surface of the electric / acoustic converter for active sound insulation, and the remaining error signal is deleted from the error detector having the sound / electric conversion function arranged on the same surface. It detects and updates the coefficient of the adaptive filter so that this error signal becomes zero,
This operation mainly prevents low-pitched noise. On the other hand, the sound absorbing material arranged on the back surface of the electric / acoustic transducer acts as a passive soundproofing device and mainly suppresses high-pitched noise.
By such an operation, it is possible to obtain a soundproofing effect from a low frequency part to a high frequency part, and it is possible to make a compact device.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A soundproofing device according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the first embodiment.
3 is a block diagram of the soundproof device in FIG. Figure 1
As shown in FIG. 1, 1 is a noise detector composed of a microphone or the like, 2 is an adaptive filter, 3 is a power amplifier, 4 is an electric / acoustic converter composed of a speaker, etc., and 4a is an electric / acoustic converter. A rectangular flat plate diaphragm arranged in the converter 4, 5 is an acoustic / electrical converter composed of a microphone or the like as an error detector, 6 is a calculator for performing convolution operation, 7 is a multiplier, and 8 is a preamplifier. , 9
Is an adder, 10 is a control device configured as a device block, and 22 is a passive soundproof wall arranged on the back surface of the electro-acoustic transducer 4. Further, the structure of the electric / acoustic transducer 4 is shown in FIG. 3 as a sectional perspective view. That is, a rectangular flat plate vibration plate 4a is arranged on the front surface, a passive soundproof wall 22 made of a sound absorbing material or the like is arranged on the rear surface, and a control device 10 as a control circuit is arranged and integrated in a space inside thereof. ing. The same functions and shapes as those of the conventional example are designated by the same reference numerals.

With respect to the soundproofing device having the above-described structure, the operation of the components will be described below. The noise detected by the noise detector 1 is signal-processed by the adaptive filter 2, passes through the power amplifier 3, and is reproduced as a sound by the vibration of the rectangular flat diaphragm 4a of the electric / acoustic converter 4, and the acoustic / electric converter It is detected at 5. This acoustic / electrical converter 5 is arranged on the same surface as the rectangular flat plate vibration plate 4a of the electric / acoustic converter 4, and the vicinity of this surface is taken as a place where noise should be removed, that is, an evaluation point. On the other hand, the noise from the noise source propagates through the space to reach this surface, and is also detected by the acoustic / electrical converter 5. The sound detected by the acoustic / electrical converter 5 detects the noise remaining in the place where the noise is desired to be canceled. That is, the signal detected by the acoustic / electrical converter 5 remains as an unerased signal and becomes an error signal.

On the other hand, the noise detection signal of the noise detector 1 is calculated by the calculator 6 which performs the convolution calculation having the control transfer characteristic C1, and the multiplier 7 multiplies it by the error signal of the acoustic / electrical converter 5 to make it adaptive. It is input to the filter 2 as a coefficient update signal so that the error signal is minimized. In this way the active noise control system operates and the error signal at the evaluation point is minimized, ie the noise is minimized.

Further, since the passive soundproof wall 22 is arranged on the back surface of the electric / acoustic converter 4, the noise from the noise source, which is mainly in the low frequency range, is the passive soundproof wall 22.
The sound is prevented by, and it becomes difficult to reach the front surface of the electric / acoustic transducer 4. In this way, the noise on the front surface of the electro-acoustic transducer 4 can be prevented from low to treble with a compact configuration.

Next, a soundproofing device according to a second embodiment of the present invention will be described with reference to FIG. As shown in FIG. 2, as its constituent elements, 1 is a noise detector composed of a microphone or the like, 2 is an adaptive filter,
3 is a power amplifier, 4 is an electric / acoustic converter including a speaker, 4b is a rectangular flat diaphragm on which the electric / acoustic converter 4 is located, and 5a is an acoustic detecting device including a microphone as an error detector. / Electrical converter, 6 is an arithmetic unit for performing a convolution operation, 7 is a multiplier, 8 is a preamplifier,
Reference numeral 9 is an adder, 10 is a control device as a block, and 22 is a passive soundproof wall. The same reference numerals are given to those having the same function and shape as those of the embodiment.

With respect to the soundproofing device having the above-described structure, the operation of the components will be described below. The noise detected by the noise detector 1 is signal-processed by the adaptive filter 2, passes through the power amplifier 3, and passes through the electrical / electrical
It is reproduced by the vibration of the rectangular flat plate vibration plate 4b provided in the acoustic transducer 4 and detected by the acoustic / electrical transducer 5a. This acoustic / electrical converter 5a is a rectangular flat plate vibration plate 4b.
Are arranged on the same plane as and have substantially the same shape. In general, a device having an electric / acoustic conversion function uses a function also having an audio / electric conversion function, and for example, a speaker is used as a microphone.

On the other hand, the noise from the noise source propagates through the space and is detected by the acoustic / electrical converter 5a. The noise that propagates through the space and reaches the evaluation point is canceled by the electric / acoustic converter 4 at the evaluation point. The signal detected by the acoustic / electrical converter 5a at this evaluation point remains as an unerased signal and becomes an error signal. On the other hand, the noise detection signal of the noise detector 1 is calculated by the convolution calculator 6 having the control transfer characteristic C1 and is multiplied by the error signal of the acoustic / electrical converter 5a by the multiplier 7, and this error signal is supplied to the adaptive filter 2. Is input as a coefficient update signal so that is minimized.

That is, the rectangular flat plate vibration plate 4b is vibrated based on the error signal detected by the acoustic / electrical converter 5a on the front surface of the electric / acoustic converter 4 to cancel the noise in the low frequency range and is arranged on the rear surface thereof. The passive soundproof wall 22 mainly shields the high frequency range to provide soundproofing. By integrating these functions, we have realized a compact and soundproof device that can prevent noise of wide frequency range. Although the rectangular flat plate vibration plate, which is a rectangular vibration plate, is used as the vibration plate of the electro-acoustic transducer 4, it goes without saying that other shapes such as a circular shape will also have the same effect.

[0015]

As is apparent from the above description, the soundproofing device of the present invention has the passive soundproof wall and the active soundproofing device integrated, and can obtain the soundproofing effect from low frequency to high frequency. Moreover, it is possible to realize a small and compact soundproofing device.

[Brief description of drawings]

FIG. 1 is a block diagram showing a partial perspective view of a soundproofing device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a partial perspective shape of a soundproofing device according to a second embodiment of the present invention.

FIG. 3 is a sectional perspective view showing the structure of the electric / acoustic transducer used in Embodiment 1 of the present invention.

FIG. 4 is a block diagram showing a partial perspective view of a conventional soundproofing device.

[Explanation of symbols]

 1 Noise Detector 2 Adaptive Filter 3 Power Amplifier 4 Electric / Acoustic Converter 4a Rectangular Plate Vibration Plate 5 Acoustic / Electric Converter 6 Calculator 7 Multiplier 22 Passive Soundproof Wall

Claims (3)

[Claims] 1. A noise detector for detecting noise from a noise source, an adaptive filter for adaptively controlling a noise detection signal detected by the noise detector, and an electric / acoustic conversion for reproducing an output from the adaptive filter. An error detector for detecting an error between a sound from a noise source and a sound from the electric / acoustic converter, and a transfer characteristic from the electric / acoustic converter to the error detector and the noise detection signal. The electric / acoustic apparatus comprises: a calculator that performs a convolution operation; and a multiplier that multiplies an output signal of the calculator and an error output from the error detector and outputs an update signal of the coefficient of the adaptive filter. The converter is a soundproof device having a thin flat plate vibration plate and the error detector on the front surface and a soundproof material on the back surface. 2. The soundproofing device according to claim 1, wherein the error detector comprises a plurality of error detectors located around the thin flat plate diaphragm. 3. A noise detector for detecting noise from a noise source, an adaptive filter for adaptively controlling a noise detection signal detected by the noise detector, and an electric / acoustic conversion for reproducing an output from the adaptive filter. An error detector for detecting an error between a sound from a noise source and a sound from the electric / acoustic converter, and a transfer characteristic from the electric / acoustic converter to the error detector and the noise detection signal. The electric / acoustic apparatus comprises: a calculator that performs a convolution operation; and a multiplier that multiplies an output signal of the calculator and an error output from the error detector and outputs an update signal of the coefficient of the adaptive filter. A soundproof device in which a converter has a plurality of thin flat plate vibration plates on a front surface, and a back surface is made of a soundproof material, and a part of the plurality of thin flat plate vibration plates operates as the error detector.