JPH10171468A - Silencer for electrical equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silencer capable of canceling random noises even when a general-use canceling speaker without excellent delay characteristic is adopted. SOLUTION: Noise from a noise source 1 typically shown by an air conditioner is detected by a microphone 2 for noise detection, and a proper filter constant corresponding to noise signal of the current noise is source is selected from a table in a storage part, and the noise outputted to a canceling loudspeaker 3 arranged forward to a testee by a distance 1 from the noise source 1 though a filter 5 changed in the characteristic by setting the constant and through the next stage amplifier 6. Otherwise, through a proper filter 5 selected from a plurality of filters comprising filter constants correspondingly to noise signal of the current noise source and through the next stage amplifier 6, the noise is outputted to a canceling loudspeaker 3 arranged forward to a testee by a distance 1 from the noise source 1. And, even if an ordinary loudspeaker without an ideal delay characteristic is used, a delay in a phase characteristic of the loudspeaker is compensated to a large extent in high a frequency range, therefore, a satisfactory muffling effect comes into play.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silencer for electric equipment such as an air conditioner or a fan for a refrigeration system.

[0002]

2. Description of the Related Art As a muffler for an air conditioner (air conditioner), which is an example of electrical equipment that generates noise, an air conditioning duct is used in theaters, conference rooms, and the like where a quiet indoor environment is required to prevent noise. Passive silencers, such as silencing chambers and sound absorbing ducts, are located at various points in the system. However, these passive silencers have been desired to be improved in terms of volume reduction in a low frequency range, pressure loss, generation of airflow noise, installation space, and the like.

Therefore, as a new means for solving these problems, there is an active noise controller which emits an additional sound having the same amplitude and opposite phase to noise and reduces the noise by the interference effect of sound waves.

FIG. 5 shows a typical example of these. In FIG. 5, reference numeral 21 denotes an air conditioning duct connected to a discharge port of the conditioned air, from which the conditioned air is sent. 22
Is a microphone that detects noise generated from the sound source, and 23 is a speaker that generates a control sound, and outputs a sound for canceling the uttered sound from the sound source. Reference numeral 24 denotes a noise-reduction microphone for detecting an error, 25 denotes a signal divider for a noise signal detected by the microphone 22, 26 denotes a digital adaptive filter (DAF) that processes the noise signal to generate a signal for generating a control sound, and 27 denotes a signal. A transfer filter that superimposes a transfer function characteristic between the muffling speaker 23 and the muffling microphone 24 on the output of the noise signal of the signal divider to correct the speaker characteristic. A transfer filter 28 outputs the output of the transfer function filter 27 and the signal from the muffling microphone 24. Least Square Operation Unit (LMS) for adjusting the coefficient of the digital adaptive filter 26 based on the
It is.

[0005] The detection outputs of the microphones 23 and 24 are low-pass filters and analog-digital (A / D).
After being converted and processed, the output to the speaker is performed through a low-pass filter after digital-to-analog (D / A) conversion of the digital output from the DAF.

The basic operation of the muffler having such a configuration is based on the information of the input (signal from the noise detecting microphone 22) X of the digital adaptive filter 26 and the output (error signal) e of the muffling microphone 24, and The coefficient of the digital adaptive filter 26 is converted to a least squares operation unit (LM) by adaptive control so that the energy is minimized.
S) It is obtained in step 28 and updated successively.

When the above method is mounted on an air conditioner,
In air conditioners using ducts, the distance between the noise source and the noise-canceling microphone is relatively large, so even if the coefficients of the digital adaptive filter are obtained by the least-squares arithmetic unit (LMS) and updated sequentially, it is possible in terms of time. However, in a separation type air conditioner that does not use a duct, the distance corresponding to the duct is as short as about 10 cm, and noise must be eliminated within this distance. In addition, it is necessary to determine the coefficients of the digital adaptive filter in a least squares operation unit (LMS) almost in real time. Therefore, a digital signal processor (DSP) capable of high-speed parallel processing compared to a microcomputer
However, since a single unit has a limited processing capability, a plurality of DSPs are required.

As another example, as an input signal, only the error signal of the noise reduction microphone is used as an input signal, and a signal obtained by compensating howling characteristics from the noise reduction speaker to the noise reduction microphone is used as a reference signal to calculate the coefficient of the adaptive filter,
In some cases, feedback control is performed by using a least square calculation unit (LMS). However, even with this type of silencer, the A / D converter, D / A converter,
Delay time occurs in the processing time of digital signal processing devices, etc.
An optimum filter coefficient could not be obtained, and noise could not be silenced for random noise.

In order to solve these problems, the present applicant has already proposed, as shown in FIG. 2, an example in which a silencer is applied to an indoor unit of an air conditioner, which is an example of electric equipment. Therefore, the outline is explained. Reference numeral 1 denotes a noise source representative of an air conditioner, reference numeral 2 denotes a microphone for noise detection, reference numeral 3 denotes a muffling speaker for generating a control sound for muffling, reference numeral 4 denotes a muffling microphone, and reference numeral 5 denotes a filter. Here, the noise detection microphone 2 is located near the noise source 1,
The sound deadening microphone 4 is arranged near the sound deadening speaker 3.

Next, a method for obtaining a constant for determining the characteristics of the filter 5 will be described with reference to FIG. 3, reference numeral 12 denotes a noise detection microphone, 13 denotes a speaker that generates a control sound, 14 denotes a muffling microphone that detects muffling of the speaker, 15 denotes a signal divider for a noise signal detected by the microphone 12, and 16 denotes a noise signal. A digital adaptive filter (DAF) 17 for generating a signal for generating a control sound by superimposing a transfer function characteristic between the muffling speaker 13 and the muffling microphone 14 on the output of the noise signal of the signal divider, Is a signal adder for adding the noise signal x and the silencing signal y to obtain an error signal e, and 18 is a transfer function filter 1
7 is a least-squares operation unit (LMS) that adjusts the coefficient of the digital adaptive filter 16 based on the output of the digital adder 7 and the error signal e from the signal adder 19.

The basic operation of the silencer having such a configuration is obtained from information on the input (signal from the noise detecting microphone 12) x of the digital adaptive filter 16 and the output y (−x) of the silencing microphone 14. The coefficients of the digital adaptive filter 16 are obtained by a least squares operation unit (LMS) 18 and updated successively by well-known adaptive control so that the energy of the error signal e is minimized. As a result, a muffling signal having an opposite phase to the noise signal is obtained.

If the main noise signal depends on the rotation speed of the blower fan, first, the rotation speed of the blower fan of the air conditioner is divided into a plurality of ranges from the lowest value to the highest value of the operation range. Rotate the blower fan in each range. For example, the operation is performed at the lowest rotational speed, and the noise x1 of the noise source 1 at that time is detected by the noise detection microphone 12, and the noise signal is input to the digital adaptive filter 16 on the one hand and to the transmission filter 17 on the other hand. After the transfer function characteristics between the sound deadening speaker 13 and the sound deadening microphone 14 are superimposed, a least squares operation unit (LMS) 18
Is supplied to one of the input terminals. Further, the other input terminal of the least squares operation unit (LMS) 18 has a muffling signal x1 + y1 (−x
1) is supplied.

A least squares operation unit (LMS) 18 obtains coefficients of the digital adaptive filter 16 by adaptive control so that the energy of the error signal e1 obtained from the information x1 and y1 is minimized. The least-squares operation unit (L) is also used for the rotation speed in the next range based on x2 and y2.
In MS) 18, coefficients of the digital adaptive filter 16 are obtained by adaptive control so that the energy of the error signal e 2 is minimized.

As described above, an appropriate filter constant is sequentially obtained for each range of the number of rotations of the blower fan, and stored in a storage unit of a control microcomputer (not shown) as a table, Prepare multiple filters consisting of constant numbers. If the table is stored in the storage unit of the control microcomputer as a table, an appropriate filter constant corresponding to the current rotation speed of the blower fan is selected from the storage unit table, and the filter constant is set. Change characteristics. When preparing a plurality of filters each having a filter constant, a filter having an appropriate filter constant corresponding to the current range of the rotation speed of the blower fan is selected.

Returning to FIG. 2, the description will be continued. The noise from the noise source 1 representatively shown in the air conditioner is detected by the noise detection microphone 2, and an appropriate filter constant corresponding to the current rotation speed of the blower fan is selected from a table in the storage unit. 5 whose characteristics are changed by setting
, And is output as an audio signal to the muffling speaker 3 via the amplifier 6 at the next stage.

Alternatively, from among a plurality of filters consisting of filter constants, to the sound deadening speaker 3 via an amplifier 6 at the next stage through an appropriate filter 5 selected according to the range of the rotation speed of the blower fan at the present time. Output as audio signal. Then, the muffling speaker 3 generates a control sound for muffling according to the noise of the noise source.

The silencer constructed as described above exhibits a certain effect, but strict conditions are required for the silencer for that purpose. In the above proposed noise reduction device in which the noise source 1 and the noise reduction speaker 3 are arranged at the same position, and the noise detection microphone 2 and the noise reduction microphone 4 are arranged in the vicinity thereof, the gain and the phase are constant with respect to the frequency as shown in FIG. When a speaker having an ideal delay characteristic is adopted as the muffling speaker 3, the muffling effect can be sufficiently exhibited.

However, it is almost impossible to produce a speaker having ideal delay characteristics as shown in FIG. Further, when a general loudspeaker having a poor delay characteristic is used as a muffling speaker, a muffling effect may not be expected.

[0019]

SUMMARY OF THE INVENTION Therefore, the present invention relates to a noise reduction device mounted on an indoor unit of such a unit-type air conditioner, in which a general speaker having a poor delay characteristic is adopted as a noise reduction speaker. An object of the present invention is to provide a noise reduction device for an air conditioner that can mute random noise using a constant number of filters corresponding to a noise signal of a noise source.

[0020]

According to a first aspect of the present invention, there is provided a noise reduction device for an electric device, comprising: means for detecting a noise signal disposed near a noise source of the electric device; and a filter for inputting the noise signal. A muffling speaker for an electric device, comprising: a muffling speaker to which an output signal of the filter is applied; and means arranged near the muffling speaker to detect the muffling signal.
The filter has a plurality of filter constants calculated so that the detected noise signal and the muffling signal have opposite phases,
This is achieved by selecting a filter constant corresponding to the current noise signal, and arranging the muffling speaker ahead of the noise source on the subject side.

Thus, based on the noise source of the electric equipment,
By selecting a proper filter constant calculated in advance and changing the filter characteristics to obtain a muffling signal that is in the opposite phase to the noise signal and applying it to the muffling speaker, mute general speakers with poor delay characteristics Even when a speaker is employed, silencing of random noise can be achieved using a constant number of filters corresponding to the noise signal of the noise source.

According to a second aspect of the present invention, there is provided a noise reduction device for an electric device, which is disposed near a noise source of the electric device, for detecting a noise signal, a plurality of filters to which the noise signal is input, and a filter for the filter. In a muffler for electric equipment, comprising a muffling speaker to which an output signal is applied, and a means arranged near the muffling speaker for detecting the muffling signal, the plurality of filters are arranged such that the detected noise signal and the muffling signal are in opposite phases. A filter having a filter constant calculated in such a manner that a filter having a constant corresponding to the current noise signal is selected, and this is achieved by disposing the muffling speaker ahead of the noise source on the subject side. Is done.

Thus, based on the noise source of the electric equipment,
Select a filter having a proper constant calculated in advance,
By changing the filter characteristics to obtain a muffling signal that has the opposite phase to the noise signal and applying it to the muffling speaker,
Even when a silencing speaker is employed as a general speaker having a poor delay characteristic, silencing of random noise can be achieved using a constant number of filters corresponding to the noise signal of the noise source.

According to a third aspect of the present invention, a silencer for an electric device is achieved by applying the silencer according to the first or second aspect to an air conditioner or a refrigerator.

In this way, in the air conditioner or the refrigeration system, an appropriate constant of the filter calculated in advance is selected based on a noise source such as a blower fan, and the filter characteristic is changed so that the noise signal is in the opposite phase to the noise signal. By obtaining a muffling signal and applying it to the muffling speaker, even if a muffled speaker is used instead of a general speaker having a poor delay characteristic,
Using a constant number of filters corresponding to the noise signal of the noise source, it is possible to mute even random noise.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An air conditioner according to an embodiment of the present invention comprises an outdoor unit installed outdoors and an indoor unit installed indoors. Connected by pipes and signal lines,
It may be a so-called separate type or an integrated type.

FIG. 1 is a block diagram showing a basic configuration of a muffler for an air conditioner according to an embodiment of the present invention. 1, the same components as those shown in FIG. 2 are denoted by the same reference numerals, 1 is a typical noise source of an air conditioner, 2 is a noise detecting microphone, and 3 is a noise detecting microphone. A muffling speaker that generates a control sound for muffling, 4 is a muffling microphone, and 5 is an analog or digital filter. Here, the noise detecting microphone 2 is arranged near the noise source 1, and the silencing microphone 4 is arranged near the silencing speaker 3.

The basic structure of the silencer shown in FIG. 1 is the same as that shown in FIG. 2 except that the silencer is arranged before the noise source. As to the method for obtaining the constant for determining the characteristic of the filter 5, the constant can be obtained by the same method as described in FIG.

In FIG. 1, a noise detecting microphone 2
, The sound is generated by the muffling speaker 3, and the muffling speaker 3 is moved forward by a distance 1 from the noise source 1 in consideration of the delay time until the sound reaches the muffling microphone 4. Since the sound is transmitted at a constant speed, the phase characteristics of the loudspeaker can be advanced at a higher frequency on the frequency axis as compared with the conventional one at the high frequency on the frequency axis. The degree to which the delay is compensated increases.

The operation of the embodiment of the present invention is as follows.
The noise from the noise source 1 representatively shown in the air conditioner is detected by the noise detection microphone 2, and an appropriate filter constant corresponding to the current noise source noise signal is stored in a table of a storage unit (not shown). From the noise source 1 via the next stage amplifier 6 via the filter 5 whose characteristic is changed by setting a constant and the sound signal to the muffling speaker 3 which is disposed forward of the subject side. Output as

Alternatively, the distance from the noise source 1 via the amplifier 6 at the next stage via the appropriate filter 5 selected according to the noise signal of the noise source at the present time from among a plurality of filters consisting of filter constants. The sound is output as an audio signal to the muffling speaker 3 disposed forward by the distance l. Since the muffling speaker 3 is disposed forward of the subject side by a distance l from the noise source 1, even if a normal speaker having an ideal delay characteristic is not used, the phase characteristic of the speaker in a high frequency range is high for the subject. , The degree of compensation for the delay is increased, so that a good noise reduction effect can be exhibited.

[0032]

As described above, the noise reduction device for an electric device according to the present invention selects and sets an appropriate filter constant calculated in advance based on the noise signal of the noise source of the electric device such as a blower fan. Alternatively, a filter having an appropriate constant calculated in advance is selected, and a filter characteristic is changed to obtain a muffling signal having a phase opposite to that of the noise signal, and put out a distance l ahead of the noise source 1 toward the subject side. By applying the noise to a silencer placed in a vertical position, it is possible to mute even random noise even if the noise signal of the noise source changes, even if a normal speaker with an ideal delay characteristic is not used. Can also be inexpensive. When applied to an air conditioner, even a unit-type air conditioner having no equivalent to a duct can perform silencing control in real time.

[Brief description of the drawings]

FIG. 1 is a basic configuration of a muffler for an air conditioner as an application example of the present invention.

FIG. 2 is a basic configuration of a conventional silencer of an air conditioner.

FIG. 3 is a block diagram for determining a filter characteristic according to the present invention.

FIG. 4 shows an ideal speaker delay characteristic.

FIG. 5 is a conventional duct type silencer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Noise source of an air conditioner 2,12,22 Microphone for noise detection 3,13,23 Silencer speaker 4,14 Silencer microphone 5 Filter 6 Amplifier 7 Fan speed 15 Signal splitter 16 Digital adaptive filter (DAF) 17 Transmission filter 18 Least Square Operation Unit (LMS) 19 Adder 21 Air Conditioning Duct 24 Error Microphone 25 Signal Divider 26 Digital Adaptive Filter (DAF) 27 Transmission Filter 28 Least Square Operation Unit (LMS)

Continued on the front page (72) Inventor Makoto Yamanaka 2-5-2-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Seishi Kawano 2-5-2-5 Keihanhondori, Moriguchi-shi, Osaka Inside Sanyo Electric Co., Ltd. (72) Inventor Shozo Sugishita 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. A means for detecting a noise signal arranged near a noise source of an electric device, a filter to which a noise signal is input, a muffling speaker to which an output signal of the filter is applied, and a muffler speaker near the muffling speaker. In the noise reduction device for an electric device, the filter includes a plurality of filter constants calculated so that the detected noise signal and the noise reduction signal are in opposite phases. A filter constant corresponding to said noise signal is selected, and said muffling speaker is arranged ahead of said noise source on the subject side. 2. A means for detecting a noise signal disposed near a noise source of an electric device, a plurality of filters to which the noise signal is input, a muffling speaker to which an output signal of the filter is applied, and a muffling speaker In a muffler for an electrical device, comprising: means for detecting a muffling signal arranged in the vicinity, the plurality of filters have respective filter constants calculated so that the detected noise signal and the muffling signal have opposite phases. And a filter having a constant corresponding to a current noise signal, wherein the muffling speaker is disposed in front of the subject with respect to the noise source. 3. The silencing device for an electric device according to claim 1, wherein the muffler is applied to an air conditioner or a refrigeration device as the electric device.