JPH02226022A - Method for measuring transfer function used in active control of noise - Google Patents

Abstract

PURPOSE:To perform control of good accuracy by removing a noise component by measuring the transfer function between a compressor and a sound receiver by driving the compressor at predetermined power supply frequency and effectuating the measuring data having frequency wherein a coherent function is a set value or more among measuring data and interpolating the effective data to calculate a transfer function. CONSTITUTION:The transfer functions between a speaker 13/a compressor 8 and a microphone 12/an auxiliary microphone 15 are measured and noise having a phase reverse to that of the noise emitted from the compressor 8 is generated from the speaker 13 on the basis of said functions to perform sound arresting control. The transfer functions between the compressor 8 and the microphone 12 as well as the auxiliary microphone 15 are measured by operating the compressor 8 at predetermined power supply frequency and, among measuring data, one wherein a coherent function is set value or more is set to effective data and calculated by interpolating the effective data. By this method, the effect of a noise component is removed.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to measurement of a transfer function used in active noise control to actively cancel out noise from a machine room housing a compressor. Regarding the method.

(Prior Art) Cooling devices that use compressors, such as refrigerators, are often installed in the living space of ordinary households.
Moreover, since it is operated continuously for 11 seasons, the noise reduction is 32FF.

In this case, the most problematic source of refrigerator noise is:
The noise comes from the machine room where the compressor and the piping system connected to it are housed. That is, in the machine room, the compressor itself generates relatively large noises (compressor motor operation, fluid noise due to compressed gas, mechanical noise from heavy machinery in the compressor groove area, etc.). The connected piping system is also affected by the vibration! This machine room noise makes up most of the refrigerator noise. Therefore, it is important to suppress the noise from the machine room. This will greatly contribute to overall noise reduction.

Therefore, in the past, as measures to reduce noise from the machine room, in addition to reducing the noise of the compressor itself (for example, adopting a rotary type compressor), improvements were made to the compressor's vibration-proof support structure, and the shape of the piping system was improved. By doing this, we aim to attenuate vibrations in the vibration propagation path, or by arranging sound absorbing and sound insulating members around the compressor and piping system, we increase the amount of absorption and noise in the machine room. Toru J JM Efforts are being made to increase the number of husbands.

However, in general, the machine room of a refrigerator has multiple openings for heat radiation because it is necessary to release the heat generated by the compressor to the outside, and noise can leak outside from these openings. It turns out. For this reason, the conventional noise reduction measures as described above naturally have their limits, and are limited in that they can only be expected to reduce the noise level by about 2 dB (A) at most.

On the other hand, in recent years, with the development of electronics application technology, especially acoustic data processing circuits and g' lightning control technology, noise reduction has been achieved by taking advantage of the sound waves. The application of active noise control technology is attracting attention. In other words, this active 1; Q control is basically:
The sound from the noise ゛h is converted into an electrical signal by a control sound receiver (e.g., a microphone) installed at a specific position, and a control sounder (e.g., a speaker) is processed based on the signal processed by this electrical signal by a calculator. ) by operating
From the sound generator, the original sound (sound from the noise source) is in reverse phase.
The idea is to attenuate the original sound by generating an artificial sound with the same wavelength and same amplitude and by causing the artificial sound and the 16i sound to interfere with each other. This will be briefly explained with reference to the following.

That is, in FIG. 8, the sound generated by the compressor S, which is the noise source, is Xs, the sound B generated by the speaker A, which is the control sound generator, is Xa, the sound received by the microphone M, which is the control sound receiver, is Xm, and the control target is 8 at point O is Xo, and the first to fourth acoustic transfer functions between the sound output and human power points as described above are CAM, GAO, GSM, GS
When O, the following equation holds true for a two-man power two-output system.

In addition, each of the above acoustic transfer functions GAM, GAO, GSM,
The meaning of GSO is that the subscript in the first stage corresponds to the input end, and the subscript in the second stage corresponds to the output side (response side).For example, in GAM, the input terminal is a human input signal to speaker A, and the output from n microphones M. vi when the signal is statically constant on the output side
It will show the Q transfer function.

Therefore, the 3Xa that should be generated by speaker A is obtained from the above equation as follows: Xa-(-GSO-Xm+GSMφXo)/<C;SH
-GAO-G50- GRAM) as j! However, in this case, since the goal is to make the sound level zero at the control point 0, it is possible to set Xo=0. As a result, X a =Xm-G! JO/ (G
SO battle GAM-GSM fist G^0). As can be understood from this equation, in order to make tXo at the controlled point O zero, the 5Xm received by the microphone M is given by G-(, SO/(GSO fistG AM-G SM◆G A
O)... (1) If the sound Xa processed by applying a filter according to the transfer function G shown in is generated from speaker 8, the control target point 0
Active control can be performed to theoretically reduce the sound level to zero, and a 7ijt calculator H is provided to carry out such processing.

Therefore, in order to determine the transfer function G, the first to fourth acoustic transfer functions CAM, GAO, GSM,
It is necessary to measure GSO, and for this measurement, a transfer function constant using fast Fourier transform (FFT) is used. In this case, the al determination of the first and second a-acoustic transfer functions CAM and GAO is performed with speaker A being driven by a white noise signal with a frequency bandwidth that is subject to active control; 4 acoustic transfer function C8H,
The GSO IPI setting is performed with the compressor S actually being driven. Incidentally, for such a measurement, an auxiliary microphone M' as a measurement receiver is installed at the control target point O.
is provided.

In this case, the above formula (1) is expressed as G −1
,/ (CAM-(GSM/G50) GAO)-1/
(GAM-GO)I-GAO) ・・・・・・(
2) and ☆, so the 3rd. Regarding the fourth acoustic transfer functions GSM and GSO, the output signal from the auxiliary microphone M' provided at the target point O is used as an input terminal, and the output signal from the microphone M is an equi-uniform acoustic transfer function GOM. If the equivalent acoustic transfer function GUM with the signal on the output side is determined by At1, it becomes equivalent to determining those 2Bg transfer functions GSM and GSO by flF+.

And gfg transfer function G AM measured in this way.

Transfer function G of the arithmetic unit H based on GUM and GAO
has been decided.

(Problem to be solved by the invention) The noise spectrum generated by driving the compressor S ((i is as shown in FIG. 9, and the noise spectrum is
It only exists at integral multiples of the rotation speed of the compressor S and integral multiples of the wave number of the power source. Therefore, in the conventional lung determination method, only the portion of the acoustic transfer function GOH that corresponds to the frequency where the spectrum is present is correct.
The current situation is that it is not possible to obtain PI data. Therefore, when performing the active control using the transfer function G determined based on the &acoustic transfer function GUM obtained in this way, if the rotational speed of the compressor S fluctuates during operation (rotation The number is above the acoustic transfer function GOH
(if there is a difference between the time of measurement and the time of actual operation), the active control becomes meaningless and the silencing effect is completely reduced.
I won't be able to even know.

In addition, when measuring the acoustic transfer function as described above, at frequencies where the noise spectrum from the compressor S does not exist (jlL), the signal at the input end (output signal from the auxiliary microphone M') also changes from the signal at the output side (the microphone M'). ) also becomes a noise signal.For this reason, the transfer function Ap1
Calculations are performed using numerical data close to zero as a denominator in the meter, and in some cases, the measurement result of the η tube transfer function may become abnormally high. 71-1 obtained in this way
The constant data is actually meaningless and has no bearing on the determination of the transfer function G, but since the dynamic range of the transfer function A-1 constant is constant, the influence of the above meaningless measurement data Other relatively small level effective acoustic transfer functions)1
The accuracy of the constant data may be inadvertently lowered, and this may lead to insufficient silencing effect during active control.

The present invention has been made in view of the above circumstances, and its purpose is to improve the accuracy of establishing a transfer function necessary to eliminate noise from a compressor by active control, and to achieve a wide frequency range that allows for fluctuations in the rotational speed of the compressor. The al constant of the transfer function used for active noise control can be improved over the entire frequency band, thereby ensuring the optimum silencing effect at all times even when the compressor rotational speed varies. lj method is provided.

C Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention provides a control sound receiver that converts sound from a compressor provided in a machine room into an electrical signal, Measurement of the transfer function of the arithmetic unit, which is necessary when active control of noise is performed by a combination of an arithmetic unit that processes a signal using a predetermined transfer function, and a control sound generator that is operated based on the processed signal. In the method of ,1
The second acoustic transfer function between the group sound generator and the aI regular receiver 2g is controlled by 9! Measurements were made with a white noise signal of a predetermined frequency bandwidth input to the sound device, and the third Hg transfer function between the compressor and the control sound receiver and the fourth Hg transfer function between the compressor and the Jll quantitative sound receiver were measured. When measuring the acoustic transfer function of the compressor with the compressor driven at a predetermined power supply frequency, there will be a plurality of one
1FJ constant data to interpolate the effective 11$1 constant data, and based on the thus interpolated third and fourth acoustic transfer functions and the first and second acoustic transfer functions, the arithmetic unit It is designed to determine the transfer function of .

(Operation) As is clear from equation (1) shown in the section (Conventional Example) above, the transfer function of the arithmetic unit can be determined based on the first to fourth acoustic transfer functions. In this case, the first and second acoustic transfer functions are obtained by inputting a white noise signal of a predetermined frequency bandwidth to each control sound generator.
Since I is constant, the degree of Δp1 constant is good over a wide frequency band. On the other hand, the third and fourth acoustic transfer functions are measured while the compressor is driven at a predetermined power frequency, so the frequency band (an integer of the compressor rotation speed) in which the noise spectrum accompanying the drive exists is data other than those (frequency bands corresponding to integral multiples of the power supply frequency) will be inaccurate. However, in this case, as mentioned above, a plurality of aF1 constant data corresponding to frequencies whose coherence function is greater than or equal to a set value among the three acoustic transfer functions given by /I−1 are converted into U effects, and their effective h1 In addition to interpolating the fixed data, the transfer function of the computing unit is determined based on the thus interpolated third and fourth acoustic transfer functions and the first and second acoustic transfer functions. The transfer function has improved accuracy over a wide il wavenumber band that allows for fluctuations in the rotational speed of the compressor, for the reasons described below.

That is, the coherence function 72 (f) is expressed by the following equation, indicates the causal relationship between the turnout patterns, and is used as an evaluation function of the determined transfer function.

7'(r)-1Gxy(1')/Gxx(r month/
(Gyy(r)/にxy” (r)1 − l Gxy(r) I ノ/fG
xx(r)-Gyy(f' month(D-L, Gxx(r)
: Input power spectrum Cyy (D : Output power spectrum Gxy(r) : Cross vector Gxy'(f') : Cross spectrum (Gx
(complex conjugate of y(f')) In this case, if the ΔN-constant transfer system is linear and there is no noise or other contamination, the output is generated only by the input, so the coherence function 72 (f) is It is always "1". On the other hand, when noise is mixed in the transmission system, the coherence function 72 (f) becomes rO
Takes a value between J and "1". In other words, the coherence function 7
2(f) becomes higher when there are fewer noise components in the measured transfer function.

Therefore, as mentioned above, the third. 1l of the fourth acoustic transfer function
Of the F1 constant data, those corresponding to frequencies where the coherence function is greater than or equal to the set value match the gWJ transfer function in a frequency band with few noise components, that is, a frequency band where a noise spectrum from the compressor exists. Therefore, the third. The fourth acoustic transfer function is relatively accurate even in a frequency band where the noise spectrum from the compressor is not distributed, and the third and fourth acoustic transfer functions obtained in this way and a wide frequency band as described above Good IP across
The transfer function of the arithmetic unit determined based on the first and second total threshold transfer functions that correspond to the j-determination degree can be treated as an accurate Δp1 constant value.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 7. Here, the noise active 1. The following describes the case where a refrigerator is used as an example of a storage target.

First, in Fig. 3 showing the overall configuration of the refrigerator, 1 is the refrigerator body, and inside this, from the top, there are 2 freezer compartments.
．． A refrigerator compartment 3 and a vegetable compartment 4 are provided. 5 is a cooler disposed at the back of the freezer compartment 2; 6 is a fan that directly supplies cold air generated by the cooler 5 to the freezer compartment 2 and the refrigerator compartment 3. Reference numeral 7 denotes a machine room formed at the lower part of the back side of the refrigerator body 1, and inside this, a rotary compressor 8, a condenser pipe 9, and a defrosting water evaporation device 10 using so-called ceramic fins are housed. .

Now, as shown in FIG. 4 (here, the illustration of the condenser vibrator 9 and the defrosting water evaporator 1 [ ] is omitted),
The machine room 7 has a rectangular opening only at its back, and this opening is closed by a machine room cover 11. At this time, machine room cover 1
1, whose peripheral edge is airtightly attached to the opening edge of the machine room 7, and an elongated rectangular heat dissipation opening 11a extending in the vertical direction is formed at the left edge in the figure. There is.

That is, when the machine room cover 11 is attached, the machine room 7 is in a closed state leaving the heat radiation opening 11a.

The machine room cover 11 is made of a material (metal such as iron) that has excellent thermal conductivity and high sound transmission loss.

Further, in FIG. 4, 12 is a control sound receiver, such as a microphone, which is placed in the machine room 7, and this is located on the opposite side of the compressor 8 from the heat dissipation opening 11a (on the right side in the figure). They are arranged so as to face each other from the side), and are provided so as to convert the sound from the compressor 8, which is a noise source, into an electrical signal. Reference numeral 1 and 3 denote a speaker 1 which is a control sound device placed in the machine room 7, and this is, for example, a speaker h (heat amount opening) on the back wall of the machine room 7 (corresponding to the bottom wall of the refrigerator body 1). It is mounted and supported in a buried manner in a portion near 11a.

As shown in FIG. 6, the speaker 13 is operated by a signal obtained by adding the electric signal from the microphone 12 to the arithmetic unit 14. Processing is performed based on the principle of silencing through active control as described in the section (Conventional Example).

Here, in the case of the refrigerator configured as described above, the level of noise generated in the machine room 7 according to the drive of the compressor 8 is as shown in FIG. .5 to 5KHz band has a property that Ff becomes large. Among these noises corresponding to the δ band, the noise on the high frequency side can be attenuated by transmission loss in the machine room cover 11, etc.
! Since fj g can be easily achieved by installing an appropriate sound absorbing member in the Ilt chamber 7, active control of noise by the microphone 12, speaker 13, and computing unit 14 as described above can be performed at frequencies below 70 IHz. This can be done as a target frequency.

In addition, when performing active noise control as described above, it is important to configure the noise in the machine room 7 so that it becomes a one-dimensional plane traveling wave, both theoretically and technically. In order to easily and accurately perform the process, tl'& is used. Therefore, in this embodiment, among the three-dimensional depth, width, and height dimensions W and H in the machine room 7 shown in FIG. One-cho-hori.

Set larger than H (specifically, W=600mm, D
"H-200 mm (setting)), the standing wave of sound in the machine room 7 is established only in the primary mode. In other words, for example, if the machine room 7 is assumed to be a rectangular cavity, The following formula holds true.

f −C−NX LX + NyLy)
10(Nz/Lz)2/2 where f is the resonance frequency (l(z), NX, Ny.

Ny is the number 11 mode in each direction of X, Y, and Z, LX, Ly
, Ly, is the τJ method (that is, W, H) in each of the x, y, and z directions in the machine room 7, and C is the speed of sound. Therefore, from the above equation, the 1-1 constant (1: find the wave frequencies fx, fy, fz) in each of the x, y, and z directions.

That is, as mentioned above, if the depth dimension D is set to 200 am, the width dimension W is set to 600 am, and the height dimension H is set to 200 am, the first constant of χ・1 in the X direction The frequency fx of the wave is Ny -NZ-0, the speed of sound is C-34
Assuming 0 m/sec, fx -34010,2)/2 =850Hz, and similarly, the frequencies fy and fz of the first standing wave in the Y and Z directions are fy-34010,6)'/2. 283H2 fz-34010,2)/2 =850Hz. As a result, the target frequency (-700H
Z) In the following, the fixed wave of noise in the machine room 7 is valid only for modes in the Yjj direction (width direction), and the noise in the machine room 7 is interpreted as a one-dimensional traveling wave in the plane. be able to. For this reason, silencing 11. by active control of noise using the speaker 13 or the like. At r, the theoretical handling of the wavefront becomes a condition, and the silencing control is performed.
You will be able to perform one step accurately.

Now, in the following, a method for determining the apl of the transfer function G of the arithmetic unit 14 necessary for the above-mentioned active control will be explained with reference to FIGS. 1 and 2.

That is, in FIG. 1, the machine room 7 of the refrigerator to be measured includes a compressor 8. In addition to microphone 12 and speaker 3, an auxiliary microphone 15, which is a 1lIII sound receiver, is provided to monitor the sound at the heat radiation opening 11a, which is a point to be controlled during active control. Also,
The 7u source of the compressor 8 is connected to be obtained from an inverter device 16 which is an edible frequency power source, so that the rotation speed of the compressor 8 can be continuously adjusted by the inverter device 16. Furthermore, 17 is a noise signal generation circuit, which is provided to generate a white noise signal having the same power over the entire frequency bandwidth to be determined by the API. Reference numeral 18 denotes a transfer function measuring device that utilizes fast Fourier transform (FFT) using a CPU, for example, which whitens the terminal Ta for human input signals and the terminal Tb for output signals, and performs the measurement based on the signals input thereto. The transfer function between the input signal and the output signal (between the ends T-Ta and Tb) is determined by 71111.

Here, the data necessary to determine the transfer function G of the arithmetic unit 14 is the data required for the transfer function 1 to the second acoustic transfer function G between the H1 speaker 13 and the auxiliary microphone 15 AO,
third acoustic transfer function GSM between compressor 8 and microphone 12, compressor 8 and auxiliary microphone 1;
5 is the fourth acoustic transfer function GSO. At this time, as is clear from equation (2) shown in the section (Conventional Example), the '3rd and 4th acoustic transfer functions GSM and GSO are equal to the equi-uniform acoustic transfer function GOM, that is, the auxiliary microphone The output signal from the microphone 15 is used as the input side, and the output signal from the 11 microphones 12 is used as the output side (response side), etc. If the Ii acoustic transfer function GOM is measured, it will be equivalent to having the blue-tone transfer functions GSM and GSO fixed by lp1. Therefore, it is sufficient to measure the first and second acoustic transfer functions CAM, AO, and equivalent acoustic transfer function GOM using the transfer function ΔP1 determiner 18.

Therefore, when the first g''J transfer function CAM is determined by A11, the white noise signal from the noise signal generation circuit 17 is input to the speaker 13 and the human input signal terminal Ta of the transfer function ΔFl determiner 18. Also, microphone 12
Connected so that the output signal from the transfer function measurement 2g18 is input to the output signal terminal Tb,
Transfer function 7 when driving the noise signal generation circuit 17 with
The measurement data by the 1P1 constant meter 18 is obtained as the first lightning transfer function CAM.

In addition, when determining the second acoustic transfer function G^0 APj, the connection state between the noise signal generation circuit 17, the speaker 13, and the human power signal terminal Ta of the transfer function AP1 determiner 18 is left as is. , when the output signal terminal Tb of the transfer function AP1 regulator 18 is connected to the output signal terminal Tb of the auxiliary microphone 15 via χ, J so that the output signal from the auxiliary microphone 15 is input manually, and when the noise signal generation circuit 17 is driven in such a connected state. transfer function a
The measurement data obtained by l constant 418 is converted into a second acoustic transfer function GA
Obtained as O. In addition, these first. Of course, when the second acoustic transfer function CAM, G^() is constant, the compressor 8 is stopped.

On the other hand, when measuring the equivalent acoustic transfer function GUM, the output signal from the auxiliary microphone 15 is
8 is input to the input signal terminal Ta, and the output signal from the microphone 12 has a transfer function 1]? It is manually connected to the output signal terminal Tb of the I determiner 18, and in this state, Jl determination is performed in accordance with the procedure shown in the flowchart of FIG.

That is, the output frequency f of the inverter device gi16 is set to the lower limit frequency fo (for example, a frequency lower than the constant r671i source frequency of the compressor 8 by a predetermined amount), and the compressor 8 is rotated at the rotation speed N. In step aS, the data measured by the transfer function measuring device 18 in this state is updated and stored, and in step b), the coherence function 72 of the period taΔ-1 constant data is extracted, and the coherence function γ' is set to the set value. It is determined whether or not this is the case (step C).

Note that the above set value is determined through an experimental 7fi value.

When rYEsJ is determined in step C, the measurement data stored in step b is validated and used as the rotation speed N. (step d), as well as the output frequency f of the inverter device 16.
The compressor 8 is driven at a rotational speed N by sweeping so that Δf increases by Δf (this Δf is set to be less than the frequency resolution of the transfer function measuring device 18) (step e).

Furthermore, when it is determined that rNOJ is present in step C, the measurement data stored in step b is invalidated in step f).
, After this, the process jumps to step d and proceeds to step e.

After this, the equivalent acoustic transfer function GOH is activated according to the height of the coherence function 72,
and the sweep of the output frequency (step I)-e
) is repeatedly executed until the output frequency f of the inverter device 16 reaches the upper limit frequency fn (for example, a frequency higher than the constant r6?Ii source frequency of the compressor 8 by a predetermined amount) (step g).

Next, a%? of the plurality of measurement data acquired in step d above? Transfer function GUM (that is, an acoustic transfer function corresponding to frequencies where the coherence function 72 is greater than or equal to the set value)
To perform linear interpolation, step h), etc.1i11
i g''J Ends the measurement of the transfer function GOH.

In addition, in FIG. 7, (a) shows an example of rough measurement data of the equivalent 8g transfer function G, and (b) and (C) show the coherence function 72 of the above measurement data and the coherence function 72 based on this coherence function 72. The data of the final equivalent acoustic transfer function GOH that has been linearly interpolated is shown.

In summary, 1. a second acoustic transfer function CAM;

Since the GAO performs Al1 constant while manually applying a white noise signal of a predetermined frequency bandwidth to each speaker 13, its )11 constant accuracy is good over a wide frequency range. On the other hand, the equivalent acoustic transfer function GOM (and thus the third and fourth acoustic transfer functions GSM).

GSO) is measured with the compressor 8 driven at a predetermined power supply frequency f, so the frequency band (corresponding to integral multiples of the compressor rotational speed and integral multiples of the power supply frequency) in which the noise spectrum associated with the drive exists is measured. Data other than the specified frequency band) will be inaccurate.

However, in this case, among the equivalent 8g transfer functions GOH determined by 4-1 as described above, the measurement data of multiple points corresponding to frequencies where the coherence function is linearly interpolated, the data of the equal l11f acoustic transfer function GMO after linear interpolation is sufficiently accurate even in the frequency band where the noise spectrum from the compressor 8 does not exist.bIn other words, the coherence function γ is an evaluation function of the measured acoustic transfer function GUH, and becomes higher when there are fewer noise components in the transfer function GOH. Therefore,
Equivalent acoustic transfer function G used for linear interpolation as described above
(JM's F1 constant data (corresponding to frequencies where the coherence function 72 is greater than or equal to the set value) coincides with the frequency band with few noise components, that is, the point where the noise spectrum from the compressor 8 exists. Therefore, these Linear interpolation of Δ-1 constant data and i etc. l111
The acoustic transfer function GOM is relatively mW even in the frequency band where the noise spectrum from the compressor 8 is not distributed.
It became a thing, and in this way it became j7 &! li acoustic transfer function GOM, and T41 and second f, which have good Jl constant accuracy over a wide frequency band as described above.
The transfer function G of the arithmetic unit determined based on the J transfer functions CAM and GAO can be treated as an accurate IPI constant value with improved accuracy over a wide frequency band that allows for fluctuations in the rotation speed of the compressor 8. As a result, when performing active noise control based on the transfer function G, even if the rotational speed when the compressor 8 is actually operated is different from the Δ-1 regular time of the transfer function G, This eliminates the possibility that the silencing effect due to active control will be insufficient as in the past.

It should be noted that the present invention is not limited to the embodiments shown above, and for example, the noise reduction χ・I phenomenon is not limited to refrigerators, but can also be applied to outdoor units of air conditioners, refrigerated showcases, etc. It may be applied and various modifications may be made without departing from the gist of the invention.

[Effects of the Invention] According to the present invention, as explained above, 111! The transfer function of the above-mentioned arithmetic unit is necessary when performing active control in which the generated sound is actively canceled by interference with the artificial sound from the control sound generator operated by the signal processed by the arithmetic unit. M
The constant accuracy can be improved over a wide frequency band that allows for fluctuations in the compressor's rotational speed, making it possible to always achieve the optimal noise reduction effect even when the compressor's rotational speed fluctuates. It has excellent effects such as:

[Brief explanation of the drawing]

Figures 1 to 7 show an embodiment of the present invention, in which Figure 1 is a layout diagram schematically showing the /l1ll constant JJ method for transfer functions, and Figure 2 is a diagram showing the above-mentioned measurement. A flowchart showing the details of the method, Fig. 3 is a longitudinal sectional view of the refrigerator, Fig. 4 is a perspective view showing the main parts of the refrigerator in an exploded state, and Fig. 5 is a diagram for explaining the dimensional relationship of the main parts of the refrigerator. FIG. 6 is a diagram schematically showing a configuration for active control of noise η in a refrigerator, and FIG. 7 is a waveform diagram showing an Apl constant of the O'9 transfer function. Fig. 8 is a schematic diagram showing the principle of noise reduction by active control (1), and Fig. 9 is a diagram showing an example of the noise level characteristics in a refrigerator. Compressor, 10 is a defrosting water evaporation device, 11 is a machine room cover 11a is a heat radiation opening, 12 is a microphone (control sound receiving n),
13 is a speaker (control sound generator), 14 is a computing unit, 15
16 is an impark device, 17 is a noise signal generation circuit, and 18 is a transfer function API regulator.

Claims (1)

[Claims] 1. The sound generated by the drive of the compressor installed in the machine room is converted into an electrical signal by a control sound receiver, and the control sound generator is operated based on the signal processed by this electrical signal by a computing unit. In the method of measuring the transfer function of the arithmetic unit used for active control in which sound radiated to the outside from the machine room is actively canceled by a first acoustic transfer function between the control sound generator and the control sound receiver, and a second acoustic transfer function between the control sound generator and the measurement sound receiver. are measured with a white noise signal of a predetermined frequency bandwidth being input to each of the control sound generators, and the third acoustic transfer function between the compressor and the control sound receiver as well as the compressor and the measurement sound receiver are measured. The fourth acoustic transfer function between interpolate those effective measurement data, and interpolate the third and fourth data
A method for measuring a transfer function used in active control of noise, characterized in that the transfer function of the computing unit is determined based on the acoustic transfer function of , and the first and second acoustic transfer functions.