JPH02225974A - Noise suppressor for cooling device - Google Patents

Abstract

PURPOSE:To exclude adverse effect produced by outside noise, stabilize active control, and hence exert silencing effect effectively by setting a transfer coefficient so that it may be zero in a frequency band other than the frequency of sound generated from a noise source. CONSTITUTION:Noise outside a machine room 1 penetrates the machine room 17 through a radiation opening 3 and is detected by a sound receiver 4. The detected sound includes many noises in a band 'n' other than a frequency band of a compressor 2's sound. To eliminate the outside noises with a computing process of a computing element 9, a transfer coefficient F is set so that it may be zero in a frequency band 'n' other than a frequency 'f' of the sound generated from the compressor 2.

Description

[Detailed description of the invention] [Objective of the invention] (Industrial application field) The present invention relates to a silencer used in a cooling device such as a refrigerator,
In particular, the present invention relates to a silencer for a cooling device that actively cancels out noise from a machine room housing a noise source such as a compressor.

(Conventional technology) For example, refrigerators are often installed in the living spaces of ordinary households and are operated continuously regardless of the season, so reducing noise is an issue. It has become. In this case, the most problematic noise FX WA from the refrigerator is the noise from the machine room in which the compressor and the piping system connected thereto are housed. In other words, in the machine room, the compressor itself makes a relatively loud noise (
Compressor motor operating noise, fluid noise due to compressed gas.

The moving mechanical elements of the compression mechanism generate mechanical noise, etc.), and the piping system connected to the compressor also generates noise due to its vibration, and such machine room noise accounts for the majority of refrigerator noise. . Therefore, suppressing the noise from the machine room greatly contributes to reducing the noise of the entire refrigerator.

Therefore, conventional measures to reduce noise from the machine room include reducing the noise of the compressor itself (for example, using a rotary compressor), improving the vibration-proof support structure of the compressor, and improving the shape of the piping system. By doing this, vibration damping in the vibration propagation path can be achieved, or
By arranging sound absorbing members and sound insulating members around the compressor and the piping system, attempts are being made to increase the amount of absorption in the machine room and to increase the noise transmission loss.

(Problem to be Solved by the Invention) Generally, the machine room of a refrigerator is provided with multiple 1m openings for heat dissipation due to the need to release the heat generated by the compressor drive to the outside. Noise will leak from the area to the outside.

For this reason, the conventional noise reduction measures mentioned above naturally have their limits, and the noise level reduction effect is at most 2 dB (A
) can only be expected.

On the other hand, in recent years, with the development of electronics application technology, especially acoustic data processing circuits and acoustic control technology, the application of active noise control technology, which reduces noise using sound wave interference, has attracted attention. has been done. That is, this active control basically converts the sound from the noise source into an electrical signal using a sound receiver installed at a specific position, and
By operating a control sound generator based on a signal processed by a calculation unit from this electrical signal, the sound generator emits a signal that is in opposite phase to the original sound (sound from the noise source) at the control target point, and has the same wavelength and same wavelength. The idea is to attenuate the bit sound by generating an artificial sound with a certain amplitude and causing the artificial sound to interfere with the original sound.

When such active noise control is used to reduce machine room noise in refrigerators, noise from outside the machine room enters the machine room through the heat radiation opening, and even this external noise is received as sound in the machine room. Therefore, the control sound generator generates a sound in which the internal noise and the external noise are vertically stacked in opposite phases. In this case, the external noise is the sound that enters the machine room, and is not the sound that is emitted to the outside.Therefore, even though there is no need to actively muffle the external noise, Since out-of-phase B with added noise is generated, active damping becomes excessive, and the out-of-phase sound from the control sound generator becomes a noise source, or the out-of-phase sound is transmitted to the receiver. If detected, active control may become unstable.

The present invention has been made in view of the above circumstances, and its purpose is to provide a silencing device for a cooling device that can eliminate the adverse effects of external noise, stabilize active control, and effectively exhibit a silencing effect. .

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention provides a sound receiver that converts sound generated from a noise source in a machine room into an electrical signal, and a sound receiver that converts sound generated from a noise source in a machine room into an electrical signal. an arithmetic unit that processes an electrical signal outputted from the machine based on a preset transfer function and converts it into an out-of-phase sound signal; It is equipped with a sound generator for 1111m that generates out-of-phase sound that actively cancels the sound radiated to the outside.
The invention is characterized in that the transfer function is determined to be zero in a frequency band other than the frequency of sound generated from the noise source.

(Function) The transfer function is determined to be zero in frequency bands other than the frequency of sound (internal noise) generated from the noise source in the machine room, so even if external noise that enters the machine room does not reach the receiver. Even if it is detected, the arithmetic processing in the arithmetic unit removes the external noise b (b) in the P1 wave number band other than the internal noise frequency, and only the internal noise component is converted into an antiphase sound signal. Therefore, the out-of-phase sound output from the control generator becomes a sound from which external noise components have been removed, and the influence of external noise is eliminated.

(Example) Hereinafter, an example in which the present invention is applied to a refrigerator will be described based on FIGS. 1 to 3.

First, in FIG. 2, reference numeral 1 denotes a machine room provided in a refrigerator main body (not shown), in which a noise source such as a compressor 2 is disposed.

Reference numeral 3 denotes a heat dissipation opening that serves as a place to muffle noise (control target point), and the machine room 1 is sealed except for this heat dissipation opening 3. 4 is a sound receiver such as a microbon placed near the compressor 2, and this sound receiver 4 detects the sound from the compressor 2 and converts it into an electrical signal according to the sound pressure spectrum. . As shown in FIG. 3, this electrical signal is input to a spectrum value digitizing circuit 7 having a low-pass filter 5 and an A/D converter 6, where the electrical signal is digitized. This digitized electric signal is processed by a computing unit 9 based on the transfer function Ft, :2ji stored in advance in the storage section 8, and converted into an anti-phase sound signal. This anti-phase sound signal is D/A'll
It is converted into an analog value through the converter 10, and is driven through the low-pass filter 11 to the speaker 12, which is a control sound generator, and the negative phase sound is emitted from the speaker 12 toward the heat radiation opening 3 side (control target point). It is now possible to In this embodiment, the speaker 12 is placed near the heat radiation opening 3, and the compressor 2 is placed near the heat radiation opening 01fH.
It is located far away from 3.

In this case, as shown in FIG. 2, the sound generated by the compressor 2 is S1, the sound generated by the speaker 12 is S2, the sound received by the receiver 4 is R1, and the heat radiation opening 3 (control point).
The sound at is R2, and the sound transfer function of each m1 of the sound output and human power points as described above is Tll, T, 21.
TI2. When T22 is assumed, the following equation holds true as a two-man power two-output system.

Therefore, the sound S2 to be generated by the speaker 12 is calculated from the above equation as follows: S2- (-Tf2-R+ + Tth@R2)/(T11
-722-TI2・T21), but in this case, the goal is to reduce the sound level at the heat radiation opening 3 to zero, so R2-
You can set it as 〇. As a result, S2-R1 dispute T
I2/ (T 1.2 ・ T21- T
11 - T22). As can be understood from this equation, in order to reduce the sound R2 at the heat dissipation opening 3 to zero, the sound R1 received by the sound receiver 4 is given by F-TI2/(T12T21-T11T22
) If the sound s2 calculated and processed by multiplying by the transfer function F is generated from the speaker 12, the sound level at the heat radiation opening 3 can be theoretically reduced to zero.

By the way, the frequency band f of the sound generated by the operation of the compressor 2 is when the power supply frequency is 50Hz (compressor 2
When the rotation speed is 2850 to 3000 "p-", f-(45 to 50)XN (N is a positive integer) and 6
0Hz (compressor 2 rotation speed is 3420 to 360
0 rp-), then f-(55~60)XN (
N is a positive integer).

However, in reality, noise outside the machine room 1 enters the machine room 1 through the heat dissipation opening 3, so that the external noise is also detected by the sound receiver 4. Therefore, the receiver 4
The sound detected by the compressor 2 is as shown in Figure 5.
The sound contains a lot of noise in the band n other than the sound frequency band f.

In this case, the external noise is the sound that enters the machine room 1, and is not the sound that is emitted to the outside, so there is no need to actively muffle the external noise. Therefore, calculating using the conventional transfer function (see Figure 4) that treats external noise as the same as the noise of compressor 2, and generating negative phase sound from the speaker 12 that takes external noise into account, would be excessively active control. On the other hand, the out-of-phase sound from the speaker 12 may become a noise source, or the sound receiver 4 may detect this out-of-phase sound, making the active control unstable.

Therefore, in this embodiment, as shown in FIG.
The transfer function F is determined to be zero in a frequency band n other than the frequency f of the sound generated from the compressor 2.

If the configuration is such that arithmetic processing is performed using such a transfer function F,
Even if external noise that has entered the machine room 1 is detected by the sound receiver S4, the calculation processing in the calculator 9 removes the external noise components in the frequency band 0 other than the frequency f of the internal noise. Only the noise component will be converted into an out-of-phase sound signal. Therefore, the out-of-phase sound output from the speaker 12 becomes a sound from which external noise components have been removed.
The influence of external noise is eliminated, active control is stabilized,
The silencing effect is effectively demonstrated.

In the above embodiment, the noise source is the compressor 2, but the present invention may be applied to other noise sources such as a cooling fan, resonance sound of pipes, etc.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings; for example, the silencer according to the present invention may be
In addition to the refrigerator, the present invention can be modified in various ways without departing from the spirit of the invention, such as being applicable to an outdoor unit of an air conditioner or a refrigerated showcase.

[Effects of the Invention] As is clear from the above explanation, the present invention has determined the transfer function to be zero in a frequency band other than the frequency of the sound generated from the noise source. Even if the noise is detected by the sound receiver, the external noise components in frequency bands other than the internal noise frequency are removed through calculation processing in the arithmetic unit, and only the internal noise component is converted into an out-of-phase sound signal. That will happen. Therefore, the out-of-phase sound emitted from the control sound generator becomes a sound from which external noise components have been removed, eliminating the influence of external noise, stabilizing active control, and effectively demonstrating the silencing effect. It has the excellent effect of

[Brief explanation of the drawing]

Figures 1 to 3 show one embodiment of the present invention. Figure 1 is a frequency characteristic diagram of a transfer function, and Figure 2 is a schematic diagram for explaining the arrangement relationship of a compressor, sound receiver, and speaker. The plan view and FIG. 3 are block diagrams showing the electrical configuration. Fig. 4 is a frequency characteristic diagram of the conventional transfer function, and Fig. 5 is a frequency characteristic diagram of the conventional transfer function.
The figure is a frequency characteristic diagram of noise detected by a sound receiver. In the drawing, l is the machine room, 2 is the compressor (noise source), 3
4 is a heat radiation opening, 4 is a sound receiver, 8 is a storage section, 9 is an arithmetic unit, and 12 is a speaker (control sound generator). Applicant Toshiba Corporation Agent Patent Attorney Sato Tsuyoshi 1 Maki's 7Wl: XL Maki Characteristics No. 1 Figure 9 Skin Calculator No. 3 /゛4 Receiver @ Device 2 Noise Volume 1゛11 Machine Room No. 22 ]

Claims (1)

[Claims] 1. A sound receiver that converts the sound generated from the noise source in the machine room into an electrical signal, and arithmetic processing of the electrical signal output from the sound receiver based on a preset transfer function to generate an out-of-phase sound signal. and a control sound generator that generates an out-of-phase sound that is driven based on the out-of-phase sound signal output from the arithmetic unit and actively cancels the sound radiated from the machine room to the outside. A silencing device for a cooling device, characterized in that the transfer function is determined to be zero in a frequency band other than the frequency of sound generated from the noise source.