JPH07253788A - Active noise reducing device - Google Patents

Abstract

PURPOSE:To prevent a futile power consumption and the generation of abnormal sound caused by the unstable operation of a control system due to diffused external sound at the outside of a duct by stopping the unnecessary operation of an active noise reducing device in the case a blower or the like being a noise source is operated in a low noise level or in the case the blower is not operated. CONSTITUTION:This device is provided with a first and second averaging means 6a, b averaging outputs of a first and second microphones 2, 3 detecting propagating noise from the noise source, a first and second storage means 7a, b storaging dark noise levels and a first and second dividing means 8a, b dividing averaging outputs of the noise levels by outputs of storage means (dark noise levels) 7a, b. Moreover, the device is provided with a first reduced amount calculating means 9a estimating a reduced amount with outputs of the first and second dividing means 8a, b, a first comparing means 10 comparing the output of the reduced amount calculating means 9a with a set value 11 equivalent to a certain reduced amount and a stopping means 12 stopping the operation of the active noise reducing device by the signal of the first comparing means 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention artificially generates a sound wave having the same amplitude as a propagating sound wave (hereinafter, referred to as "propagating noise") of a noise source but having a phase opposite to that of the propagating noise. The present invention relates to an active noise reduction device that suppresses noise by mutual interference.

[0002]

2. Description of the Related Art FIG. 9 is a diagram showing an air conditioning system having a fan as a noise source in the conventional active noise reduction device disclosed in Japanese Utility Model Laid-Open No. 63-45599. In the illustrated air conditioning system, a blower 51 for taking in and transporting air and a heat exchanger 52 for adjusting the taken air to a certain temperature are installed in the air conditioning duct 1, and outside the air conditioning duct 1. Compressor unit 5 including a compressor for supplying a refrigerant adjusted to a temperature (pressure) in the heat exchanger 52
3 and a central control unit 54 for an air conditioning system that controls the rotational speeds of the blower 51 and the compressor unit 53 and issues a drive command for these. When the blower 51 is driven, air is taken in and transported, and noise is generated. This noise propagates through the air-conditioning duct 1 and propagates to rooms (noise-exposed areas) that require air conditioning. In order to reduce the propagated noise, a passive noise reduction material (or silencer) such as the sound absorbing material 55 or an active noise reduction device described in detail below is used. Generally, passive silencers are effective for noise in the mid- and high-frequency bands above 500 Hz,
The active noise reduction device is considered to be effective in reducing noise in the low frequency band of 50 to 500 Hz. Next, the configuration of the active noise reduction device will be described. A first microphone 2 and a second microphone 3 for evaluating the noise reduction effect are installed on the downstream side of the installation position of the first microphone 2 in the air conditioning duct 1 serving as a sound wave propagation path. Has been done. Furthermore, the first and second microphones 2, 3
A mute speaker 4 is provided between them. Also, the first
A control circuit 5 is provided between the microphone 2 and the muffler speaker 4, and the control circuit 5 includes a stop means 12 for stopping the operation of the active noise reduction device. The stopping means 12 is stopped and stopped (operated) in response to a command signal from the central control unit 54 for an air conditioning system.

Next, the operation will be described. In the above-described configuration, the blower 51 and the compressor unit 53 of the air conditioning system start operating in response to the operation and the rotation speed command of the central control unit 54 for the air conditioning system, and each operates at a predetermined rotation speed. The compressor unit 53 supplies the refrigerant of a certain temperature (pressure) set based on the rotation speed command to the heat exchanger 52 via the refrigerant pipe. On the other hand, the blower 51 similarly takes in a required amount of air into the air conditioning duct 1 based on the rotation speed command. The introduced air of a certain temperature is heat-exchanged with the refrigerant from the compressor unit 53 in the heat exchanger 52, adjusted to the set air temperature, and is supplied to a room where air conditioning is required. Only the required amount of air is transported. The rotation speed of the blower 51 is controlled according to the required air volume. With the operation of the blower 51, the blower 51 becomes a noise source, and the noise propagates in the air conditioning duct 1 together with the air and reaches the room. Further, the noise generated due to the change in the rotation speed of the blower also changes. FIG. 2 is a diagram showing how the noise level (solid line X) of the blower changes when the rotation speed of the blower changes with time. In order to reduce the noise of such an air-conditioning system in a noise-exposed area such as a room, the air-conditioning duct 1
Noise reduction measures are implemented by installing a noise reduction means such as a passive silencer 55 made of a sound absorbing material effective in the middle and high frequency regions and an active noise reduction device effective in the low frequency region.

The operation of the active noise reduction device which is the noise reduction means will be described. The stop means 12 for stopping the operation of the active noise reduction device is a manual switch built in the control circuit 5 (including the power supply means of the control circuit) or an external signal, for example, an operation operation signal of a rotating machine (such as a blower). And the active noise reduction device starts operating. Here, the operation operation of the active noise reduction device is shown to be operated by the operation operation command of the centralized control device 54 for the air conditioning system. First, the propagation noise is detected by the first microphone 2, converted into an electric signal, and input to the control circuit 5. In response to this signal, the control circuit 5 generates a muffling electric signal having the same amplitude but opposite phase, and outputs it to the muffling speaker 4. The muffling speaker 4 converts this electrical signal into a mechanical signal and radiates a muffling sound wave. Here, the propagating noise and the sound wave for silencing interfere with each other and are combined to mute, but due to the difference in acoustic conditions in the propagation path,
The sound is not muted sufficiently. Therefore, a second microphone 3 for evaluating the muffling effect is installed, and at that position, the second microphone 3 is set so that the sound pressure level due to the mutual interference between the muffling sound wave radiated from the muffling speaker 4 and the propagation noise becomes zero. The output signal of is input to the control circuit 5, the control system is fed back to correct the control coefficient, and the drive signal is given to the muffling speaker 4 again so that the sound pressure level of the second microphone 3 becomes close to zero. To do. By repeating this operation, a sufficient silencing effect is obtained.

[0005]

The conventional active noise reduction device is constructed as described above, and the operation operation of the active noise reduction device is performed by operating the central control unit 54 for the air conditioning system installed far from the active noise reduction device. Operation command, for example, the same signal as the power supply of the centralized control device, operation command of the blower / compressor, and the control circuit 5 that is an active noise reduction device
It is done by operating the built-in manual switch,
Further, it is often performed at the same time as the power supply to the control circuit 5. Considering the case where the command signal from the centralized control unit 54 is the same signal as the power supply to the centralized control unit, the information on the operating state of the blower, which is the noise source, is not transmitted, so the operation of the blower is stopped. However, the active noise reduction device continues to operate. In addition, if it is due to the operation signal of the blower that is the noise source, even if the active noise reduction device can operate at the same time as noise is generated, the operating point of the blower (air volume, total pressure, rotational speed, etc.) In any state, for example, when the noise level is close to the background noise level (X) at times T3 to T4 in FIG. 2 or when the noise is audible or not at times T5 to low, That is, the active reducing device always operates regardless of the noise level in the duct. Therefore, the active noise reduction device operates even when the blower is operating at a low noise level operating point or when there is not much need to reduce noise, such as when the blower is not operating. There is a problem of consuming.

Further, since the active noise reduction device is operating even when the rotating machine such as the blower is operating at a low noise level or when the blower is not operating, the impact noise from the outside of the duct, etc. The active noise reduction device reacts due to the disturbance, the operation of the control system becomes unstable, and when it deteriorates, the control system diverges and an abnormal sound is generated from the muffling speaker 4. Therefore, the active noise reduction device reversely operates the noise generation device. There is a problem that becomes.

The present invention has been made in order to solve the above-mentioned problems, and produces noise when a blower which is a noise source is operating and when a blower which is a noise source is not operating. The ratio of background noise is calculated, the noise reduction amount is calculated and estimated based on this value, and the estimated noise reduction amount is lower than a certain noise reduction amount (level when active noise reduction is necessary and possible). In this case, it is an object of the present invention to provide an active noise reduction device that does not consume unnecessary power by stopping the active noise reduction device.

Further, when the blower, which is a noise source, is operating at a low noise level, the control operation of the active noise reduction device becomes unstable due to the disturbance noise from the outside of the duct, and an abnormal sound is generated from the muffling speaker. Therefore, the noise reduction amount is calculated based on the ratio of the noise to the background noise when the noise source blower is operating and when the noise source blower is not operating. When the estimated noise reduction amount is lower than a certain noise reduction amount (level when active noise reduction is necessary and possible), the operation of the active noise reduction device is stopped An object of the present invention is to provide an active noise reduction device that prevents the generation of sound.

[0009]

According to a first aspect of the present invention, there is provided an active noise reduction device, wherein a sound pressure of a first microphone provided for detecting a sound wave propagating from a noise source is converted into an electric signal. A) first averaging means for averaging the output signal, and averaging the noise (background noise) at the first microphone point when the noise source is not driven by the first averaging means, A first storage means for storing the output signal,
A first signal for averaging the noise generated when the noise source is driven by the first averaging means to generate a division signal of the output signal of the first averaging means and the output signal of the first storage means. An output signal (sound pressure converted into an electric signal) of the second microphone, which includes a dividing means and detects a composite sound wave of the sound wave propagating from the noise source and the sound wave radiated from the muffling speaker, is averaged. Second averaging means and noise (background noise) at the second microphone point when the noise source is not driven
Is averaged by the second averaging means, and a second storage means for storing the output signal thereof is provided, and the noise when the noise source is driven is averaged by the second averaging means, Two
Second division means for generating a division signal of the output signal of the averaging means and the output signal of the second storage means, and the estimated noise reduction by the output signals of the first division means and the second division means. A first reduction amount calculating means for calculating an amount, and a first comparison for comparing an output signal of the first reduction amount calculating means with a set value corresponding to a certain noise reduction amount of the first level setting means. And the operation of the active noise reduction device is stopped in response to the output of the means and the first comparison means.

Further, in the active noise reduction apparatus according to claim 2 of the present invention, the output signal (sound pressure converted into an electric signal) of the first microphone provided for detecting the propagating sound wave from the noise source. To a first filter means having a certain characteristic to average the output of the first filter means, and a first averaging means when the noise source is not driven.
Noise at the microphone point (background noise) is averaged by the first averaging means and the output signal thereof is stored, and the noise when the noise source is driven is determined by the first averaging means.
The first averaging means for averaging to generate a division signal of the output signal of the first averaging means and the output signal of the first storing means, and the propagation from the noise source. An output signal (sound pressure converted into an electric signal) of a second microphone that detects a composite sound wave of a sound wave and a sound wave emitted from the silencer speaker is input to a second filter means having a certain characteristic, Second averaging means for averaging the outputs of the second filter means and noise (background noise) at the second microphone point when the noise source is not driven are averaged by the second averaging means. Second, which stores the output signal
And storing the noise when the noise source is driven by the second averaging means, and dividing the output signal of the second averaging means by the output signal of the second storing means. And a second division means for generating the first division means and the second division means.
Corresponding to a certain noise reduction amount of the first reduction amount calculation unit for calculating the estimated noise reduction amount by the output signal of the division unit, and the output signal of the first reduction amount calculation unit and the first level setting unit. The first comparison means for comparing the set value to be set and the operation of the active noise reduction device are stopped in response to the output of the first comparison means.

According to a third aspect of the present invention, in the active noise reduction device, the first microphone provided to detect the sound wave propagating from the noise source, the sound wave propagating from the noise source, and the radiation from the silence speaker. The second which detects the synthetic sound wave with the sound wave
First switching means for switching the output signal (converted into an electric signal from the sound pressure) with the microphone of
First averaging means for averaging the output signals of the microphones, and noise (background noise) at the first or second microphone point when the noise source is not driven to the first averaging means. And second averaging means for respectively averaging and storing the output signals thereof, and the first and second memorizing means.
Second switching means for switching the output of the storage means, and the output signal of the first storage means or the second storage means and the first
First dividing means for generating a divided signal with the output signal of the averaging means, the output signal of the first storing means (background noise at the first microphone point), and the output signal of the first averaging means. A third storage unit for storing a division calculation force signal with (the noise of the first microphone) is provided, and an output signal calculated by the first division unit for the ratio of the noise of the second microphone to the background noise and the output signal A third reduction amount calculation unit for calculating an estimated noise reduction amount by an output signal of the storage unit 3 (a divided value of noise of the first microphone and background noise), and an output signal of the first reduction amount calculation unit. And a first comparison means for comparing a set value corresponding to a certain noise reduction amount of the first level setting means, and an operation of the active noise reduction device upon receiving the output of the first comparison means. It is the one.

According to a fourth aspect of the present invention, in the active noise reduction device, a first microphone (or a sound wave propagating from the noise source and the muffler speaker) provided for detecting the sound wave propagating from the noise source is used. A second microphone for detecting a synthesized sound wave of the emitted sound wave and a first averaging means for averaging the output signal (sound pressure converted into an electric signal) of the second microphone, and a case where the noise source is not driven. When the noise source is driven by the first storage means for averaging the noise (background noise) at the first (or second) microphone point by the first averaging means and storing the output signal thereof First noise for averaging the noise of the first averaging means to generate a division signal of the output signal of the first averaging means and the output signal of the first storage means.
Second reduction amount calculating means for calculating an estimated noise reduction amount by the output signal of the first dividing means, an output signal of the second reduction amount calculating means, and a first level setting. The means for comparing the set value corresponding to a certain noise reduction amount of the means, and the operation of the active noise reduction device upon receiving the output of the first comparison means.

According to a fifth aspect of the present invention, in the active noise reduction device, the output signal (sound pressure converted into an electric signal) of the first microphone provided for detecting the propagating sound wave from the noise source. And a noise (background noise) at the first microphone point when the noise source is not driven by the first averaging means and outputs the output signal. A wind speed (air volume) detecting means provided to detect a wind speed (air volume) in the propagation path of the sound wave when a noise source is driven,
(Air volume) Wind speed (noise) -electric conversion equivalent averaging means for converting and averaging into an electric signal corresponding to output signal of detecting means, output signal of first storage means and wind speed (noise) -electric conversion averaging means Second division amount calculation means for calculating an estimated noise reduction amount by the output signal of the first division means, and the second reduction means. A first comparing the output signal of the amount calculating means with a set value corresponding to a certain noise reduction amount of the first level setting means.
And the operation of the active noise reduction device is stopped in response to the outputs of the comparison means and the first comparison means.

According to a sixth aspect of the present invention, in the active noise reducing apparatus, the output signal (sound pressure converted into an electric signal) of the first microphone provided for detecting the sound wave propagated from the noise source. And a noise (background noise) at the first microphone point when the noise source is not driven by the first averaging means and outputs the output signal. A wind pressure detecting means, which is provided with a first storing means for storing, and is provided for detecting the wind pressure in the propagation path of the sound wave when the noise source is driven; and an electric signal corresponding to the noise level of the signal of the wind pressure detecting means. Wind pressure (noise) to be converted and averaged into a signal-electric conversion averaging means, and a first signal for generating a division signal of the output signal of the first storage means and the wind pressure (noise) -output signal of the electric conversion averaging means Division means and an output signal of the first division means The second reduction amount calculation means for calculating the estimated noise reduction amount, the output signal of the second reduction amount calculation means, and the set value corresponding to a certain noise reduction amount of the first level setting means. The first comparing means for performing the operation and the operation of the active noise reduction device are stopped in response to the output of the first comparing means.

Further, in the active noise reduction device according to claim 7 of the present invention, the output (converted into an electric signal of sound pressure) of the first microphone provided for detecting the sound wave propagated from the noise source. First averaging means for averaging the signals, and noise (background noise) at the first microphone point when the noise source is not driven by the first averaging means, and the output signal thereof. And a rotation speed detection means provided for detecting the rotation speed of the rotating machine when the rotating machine, which is a noise source, is driven, and a signal of the rotation speed detection means is used as a noise level. Number of revolutions (noise) converted into an electric signal corresponding to averaging-electric conversion averaging means, and the output signal of the first storage means and the number of revolutions (noise) -output signal of electric conversion averaging means First dividing means for generating a signal, said first dividing means Second reduction amount calculation means for calculating the estimated noise reduction amount by the output signal of the stage, output signal of the second reduction amount calculation means, and setting corresponding to a certain noise reduction amount of the first level setting means A first comparison means for comparing a value with the first comparison means and an operation of the active noise reduction device are stopped by receiving the output of the first comparison means.

[0016]

In the active noise reduction device according to the first aspect of the present invention, the noise (background noise) when the noise source is not driven at the points of the first and second microphones 2 and 3 is stored, A ratio (noise to background noise ratio) between the background noise level and the noise level when the noise source is driven is calculated, and the reduction amount or coherence is estimated by the reduction amount calculation means based on the value, and a certain setting is made. Level (for example, 3-5 for reduction amount)
dB and coherence are 0.5 to 0.68), and if the value is equal to or less than the set value (when noise reduction by the active noise reduction device is unnecessary), the operation of the active noise reduction device is stopped and wasteful. The power consumption is suppressed, and the generation of abnormal sound due to the unstable operation of the control system due to disturbance is prevented.

Further, in the active noise reduction apparatus according to claim 2 of the present invention, as means for detecting the background noise level and the noise level, filter means having a certain characteristic, for example,
A hearing-aware correction characteristic (A characteristic, etc.) or an active noise control frequency range band-limited to 50 to 500 Hz is provided to improve the detection accuracy of the noise-to-background noise ratio more appropriate for the active noise reduction device. Is.

Further, in the active noise reduction apparatus according to claim 3 of the present invention, the averaging means and the dividing means are shared by switching the output signals of the first microphone 2 and the second microphone 3. This is a simplification of the circuit.

Further, in the active noise reduction device according to claim 4 of the present invention, the blower which is a noise source is driven by either one of the first microphone 2 and the second microphone 3. The noise reduction amount is estimated based on the value of only one side, assuming that the ratio of the noise when the vehicle is stopped and the noise level when it is stopped (noise-to-background noise ratio) is approximately the same level, resulting in a significant circuit reduction.

Further, in the active noise reduction apparatus according to claim 5 of the present invention, the noise level of the noise source is estimated by the wind speed of the blower without using the microphone, thereby reducing the influence of noise due to wind or the like, This is intended to improve the detection accuracy of the noise-to-background noise ratio.

Further, in the active noise reduction apparatus according to claim 6 of the present invention, the noise level of the noise source is estimated by the wind pressure of the blower instead of the microphone, thereby reducing the influence of noise due to wind or the like, This is intended to improve the detection accuracy of the noise-to-background noise ratio.

In addition, in the active noise reduction device according to the seventh aspect of the present invention, the noise level of the noise source is estimated by the rotation speed of the blower without using the microphone, thereby reducing the influence of noise due to wind or the like. Therefore, the detection accuracy of the noise-to-background noise ratio is improved.

[0023]

【Example】

Example 1. 1 is a diagram showing a system of an active noise reduction device according to a first embodiment of the present invention. In the air conditioning system shown in the figure, a blower 51, a heat exchanger 52, a compressor unit 53, an air conditioning system centralized control device 54, a sound absorbing material 55, a first microphone 2 which is an active noise reduction device, a second microphone 3, and a muffler. Since the speaker 4 and the control circuit 5 have the same configuration and operation as those of the conventional example, the description thereof will be omitted, and the components related to the present invention will be described in detail. The configuration of the active noise reduction device of the present invention averages the output signal (sound pressure converted into an electric signal) of the first microphone 2 provided for detecting the propagating sound wave from the blower 51 which is a noise source. The first averaging means 6a for averaging and the noise (background noise) at the point of the first microphone 2 when the blower 51 as a noise source is not driven are averaged by the first averaging means 6a. , First storing its output signal
Of the output signal of the first averaging means 6a and the first memorizing means for averaging the noise when the blower 51 as the noise source is driven by the first averaging means 6a. The blower 51 is provided with a first division means 8a for generating a division signal with the output signal of the means 7a, and which is the noise source.
Second averaging means 6b for averaging an output signal (sound pressure converted into an electric signal) of the second microphone 3 for detecting a composite sound wave of the propagated sound wave from the sound source and the sound wave radiated from the silence speaker 4. And the noise (background noise) at the point of the second microphone 3 when the blower 51 which is the noise source is not driven is averaged by the second averaging means 6b and the output signal thereof is stored. The second averaging means 6b averages the noise generated when the blower 51, which is a noise source, is driven by the second averaging means 6b, and the output signal of the second averaging means 6b and the second memory. A second division means 8b for generating a division signal with the output signal of the means 7b is provided, and by the output signals of the first division means 8a and the second division means 8b,
It corresponds to a certain noise reduction amount of the first reduction amount calculation means 9a for calculating the estimated noise reduction amount or the estimated coherence, the output signal of the first reduction amount calculation means 9a and the first level setting means 11. The configuration is such that a first comparing means 10 for comparing a set value and a stopping means 12 for receiving the output of the first comparing means 10 and stopping the operation of the active noise reduction device are provided.

Next, the operation of the present invention will be described. First, when the blower 51, which is a noise source, is not driven, the noise (background noise) at each point of the first microphone 2 and the second microphone 3 is reduced by the first and second averaging means 6a, 6b is averaged, and the output signal is stored in the first and second storage means 7a and 7b. Next, the first microphone 2 when the blower 51, which is a noise source, is driven
The noises at the respective points of the second and third microphones 3 are averaged by the first and second averaging means 6a, 6b and input to the first and second dividing means 8a, 8b. The first and second dividing means 8a and 8b calculate the noise level to background noise level ratio at the points of the first and second microphones. The output signals of the first and second dividing means 8a and 8b are input to the first reduction amount calculating means 9a. In the first reduction amount calculating means 9a, first, the coherence γ ² is calculated from the equation (1-1).
To calculate.

[0025]

[Equation 1]

Next, the estimated reduction amount ΔSPL is calculated by the equation (1-2) from the calculation result of the equation (1-1). ΔSPL = -10 × Log (1-γ ² ) ... (Equation 1-2) Operation value of (Equation 1-2), that is, first reduction amount operation means
The output value (signal) of 9a is input to the first comparison means 10, and the first comparison means 10 causes the first level setting means 11 to
Compared with a certain noise reduction amount-for example, a set value from 3 dB which is a limit sound pressure level difference which can be recognized by humans to 5 dB which is a sound pressure level difference which can be clearly recognized by humans- When it is lower than the level setting means 11 of 1, the stop signal 12 in the active noise reduction device is operated by the output signal of the first comparison means 10 to stop the operation of the active noise reduction device, resulting in unnecessary power consumption. This is to suppress the generation of abnormal sound due to unstable operation. The operation of the active noise reduction system according to the present invention is shown in FIG. The horizontal axis represents time, and the vertical axis represents the noise level of the blower 51, which is a noise source.
The solid line X shows the temporal transition of the noise level of the blower 51, which is the noise source, and the broken line Y is the noise level corresponding to the setting level of the first level setting means. Blower 5 at the bottom of the figure
1 and active noise reduction device (displayed as ANC) ON / O
FF is described. During the period from time T0 to T1 on the solid line X, the background noise level is when the blower 51, which is a noise source, is not driven, and the active noise reduction device is also stopped. At times T2 to T3, the rotation speed of the blower becomes high (when a large amount of air is required), the noise level rises, and the noise of the blower increases to the level of the point Y (broken line) where the active noise reduction device operates. Works. At this time, the noise level (particularly the point of the second microphone 3) is detected by suspending the operation of the active noise reduction device for a certain period of time for a moment. After that, the rotational speed decreases (when the air volume is reduced), and the active noise reduction device stops at times T3 to T4 below the broken line Y. As a result, it is possible to suppress unnecessary power consumption of the active noise reduction device when the noise level is low and generation of abnormal noise due to reaction of the active noise noise reduction device due to disturbance noise.

Example 2. FIG. 2 is a diagram showing a system of an active noise reduction device according to a second embodiment of the present invention. The configuration of this air conditioning system is such that filter means 13a and 13B are provided between the first and second microphones 2 and 3 and the first and second averaging means of the first embodiment. The filter characteristic of the filter means is the frequency correction circuit (A
Characteristics, etc.-Reference example: JIS C 1505 Precision sound level meter) or the control range of the active noise reduction device, for example, 50 to
For example, a bandpass filter having a characteristic of 500 Hz or a combination of the former and the latter. As for the operation, in the frequency correction circuit characteristic (for example, A characteristic) of the sound level meter as the filter characteristic, attention is paid only to the noise that contributes to human hearing, or when the band pass filter characteristic (for example, 50 to 500 Hz) in the control range of the device is used. This is to consider only the controllable range of the active noise reduction device, and to further improve the operating conditions of the active noise reduction device and the detection accuracy of the noise-to-background noise ratio. The configuration and operation of the other parts are the same as those in the first embodiment, and will be omitted.

Example 3. Although the reduction amount is estimated by the first reduction amount calculating means 9a in the first embodiment, the coherence may be estimated, and the calculation amount can be reduced. In this case, the setting level of the first level setting means 11 has a coherence value of 0.5 to 0.65 if the reduction amount is 3 to 5 dB.

Example 4. In the first embodiment, the first and second averaging means 6a and 6b, the first and second storage means 7a and 7b, the first and second dividing means 7a and 7b, and the first reduction amount calculation. Although the means 9a, the first comparing means 10, and the first level setting means 11 are shown separately, the calculating means including all of them may be used.
Also, a part of these may be included. For example, the first and second division means 8a and 8b and the first reduction amount calculation means 9a are combined into one calculation means. Further, these means may be analog circuits, digital circuits (including software), or a mixture thereof.

Example 5. In the first embodiment, the background noise level at the points of the first and second microphones 2 and 3 was initially detected. However, the background noise level can be detected at any time when the blower 51, which is a noise source, stops. It is also possible to adopt a configuration in which the accuracy is improved with respect to the level temporal fluctuation.

Example 6. It should be noted that the comparison means 10 of the above-mentioned Example 1 is required to have hysterisis characteristics,
By providing the time delay means in the subsequent stage, it is possible to suppress the pulsation of the output signal of the means 12 for stopping the operation of the active noise reduction device and obtain a more stable operation of the active noise reduction device. .

Example 7. In the first embodiment, the active noise reduction device in the air conditioning duct is shown, but other application examples are also possible, and two microphones and a speaker 1 are used.
It does not have to be a single system, but it is a feedforward type active system that generates a sound wave for silencing of the same amplitude in opposite phase to the propagating noise and mutes it by mutual interference with the propagating noise, such as one using a plurality of the above devices. Any noise reduction device may be used.

Example 8. Although the sound wave signal is detected by the microphone in the first embodiment, a mechanical-electrical conversion means may be used as long as it is a vibration having a correlation with a sound wave, and an electro-mechanical conversion means may be used instead of the sound deadening speaker.

Example 9. Although the operation of the control circuit 5 of the active noise reduction device is stopped in FIG. 1 of the first embodiment, a method of stopping the operation of the silence speaker 4 may be used.

Example 10. FIG. 4 is a diagram showing a system of the active noise reduction device according to claim 3 in the tenth embodiment of the present invention. In the air conditioning system shown in the figure, a blower 51, a heat exchanger 52, a compressor unit 53, an air conditioning system centralized control device 54, a sound absorbing material 55, and an active noise reduction device
Since the microphone 2, the second microphone 3, the muffler speaker 4, and the control circuit 5 have the same configuration and operation as those of the conventional example, the description thereof will be omitted and the components related to the present invention will be described in detail. According to the configuration of the active noise control device of the present invention, the first microphone 2 provided for detecting the sound wave propagated from the blower 51, which is a noise source, the sound wave propagated from the noise source, and the sound wave radiated from the muffling speaker. First switching means 1 for switching between an output signal (sound pressure converted into an electric signal) of a second microphone 3 for detecting a synthetic sound wave.
4a, first averaging means 6a for averaging the output signals of the first or second microphones 2 and 3, and the first or second microphone 2 when the blower 51 as a noise source is not driven. , 3 noises (dark noises) are averaged by the first averaging means 6a, and output signals thereof are respectively stored, and first and second storage means 7a, 7b are provided. Second switching means 14b for switching the outputs of the storage means 7a and the second storage means 7b, and the first storage means 7
a or a first division means 8a for generating a division signal of the output signal of the second storage means 7b and the output signal of the first averaging means 6a, and the output signal of the first storage means 7a (first The background noise at the microphone point) and the output signal of the first averaging means 6a (noise of the first microphone) are included in the third storage means 7c for storing the de-computation force signal. The estimated noise reduction amount or the estimated coherence is determined by the output signal of the ratio of background noise calculated by the first dividing means 8a and the output signal of the third storage means 7c (the divided value of the noise of the first microphone and the background noise). A first reduction amount calculating means 9a for calculating the following, an output signal of the first reduction amount calculating means 9a, and a first setting value corresponding to a certain noise reduction amount of the first level setting means 11 are compared. Comparing means 10
And a stop means 12 for stopping the operation of the active noise reduction device in response to the output of the first comparison means 10.

Next, the operation of the present invention will be described. First, when the blower 51, which is a noise source, is not driven, the first switching unit 14a is set to the first microphone side,
The noise (background noise) at the point of the first microphone 2 is averaged by the first averaging means 6a, and the output signal thereof is the first
It is stored in the storage means 7a. Next, the first switching means 14
The noise (background noise) at the point of the second microphone 3 is set to the first averaging means 6a by setting a to the second microphone side.
Are averaged and the output signal is stored in the first storage means 7b. Next, when the blower 51, which is a noise source, is driven,
On the first microphone 2 side of the first switching means 14, the noise at the point of the first microphone 2 is averaged by the first averaging means 6a and input to the first dividing means 8a. Next, the second switching means 14b is replaced with the first storage means 7.
The output signal of the first storage means 7a is input to the first division means 8a on the a side. The first dividing means 8a calculates the ratio of the output signal of the first averaging means 6a and the output signal of the first storing means 7a, that is, the ratio of the noise at the point of the first microphone 2 to the background noise, The output signal is stored in the third storage means 7c. Next, with the first switching means 14a on the second microphone 3 side and the second switching means 14b on the second storage means side, the noise and background noise ratio of the second microphone 3 are set to the first average. Conversion means 6a and second storage means 7
The output signal of a is input to the first dividing means 8a and calculated. The ratio of the noise of this second microphone 3 to the background noise,
The third, which is the ratio of the noise on the first microphone 3 side to the background noise
Output signal of the storage means 7c of the first reduction amount calculation means 9a
To calculate the estimated reduction amount or estimated coherence value. The output signal of the first reduction amount calculating means 9a is input to the first comparing means 10, and the output signal of the first level setting means 11
Compared with a certain noise reduction amount, first reduction amount calculation means 9a
When the output of the active noise reduction device is small, the stop means 12 in the active noise reduction device is operated to stop the operation of the active noise reduction device so as to suppress the generation of abnormal noise due to unnecessary power consumption and unstable operation. Is. The arithmetic expression of the first arithmetic means and FIG.
Since the operating states of the blower 51 and the active noise reduction device shown in FIG. The circuit is simplified by sharing the circuit means as compared with the case of the first embodiment.

Example 11. It should be noted that FIG.
Then, the signal of the noise to background noise ratio of the first microphone 2 is stored in the third storage means 7C.
The noise-to-background noise ratio signal may be used.

Example 12 FIG. 5 is a diagram showing a system of an active noise reduction device according to claim 4 in a twelfth embodiment of the present invention. In the air conditioning system shown in the figure, a blower 51, a heat exchanger 52, a compressor unit 53, an air conditioning system centralized control device 54, a sound absorbing material 55, and an active noise reduction device
Since the microphone 2, the second microphone 3, the muffler speaker 4, and the control circuit 5 have the same configurations and operations as those of the conventional example, the description thereof will be omitted and the components related to the present invention will be described in detail. The configuration of the active noise reduction device of the present invention averages the output signal (sound pressure converted into an electric signal) of the first microphone 2 provided for detecting the propagating sound wave from the blower 51 which is a noise source. The first averaging means 6a for averaging and the noise (background noise) at the point of the first microphone 2 when the blower 51 as a noise source is not driven are averaged by the first averaging means 6a. A first storage means 7a for storing the output signal thereof is provided, and the noise when the blower 51, which is a noise source, is driven is averaged by the first averaging means 6a, and the first averaging means 6a. Of the first storage means 7a and a first division means 8a for generating a division signal of the output signal of the first storage means 7a.
A second reduction amount calculation means 9b for calculating an estimated noise reduction amount based on the output signal of a and the second reduction amount calculation means 9b.
Of the first level setting means 11 and a setting value corresponding to a certain noise reduction amount of the first level setting means 11
0 and a stop means 12 for stopping the operation of the active noise reduction device in response to the output of the first comparison means 10.

Next, the operation of the present invention will be described. Although the same operation as in the first embodiment is performed, in the present invention, it is considered that the noise ratio of the first microphone and the second microphone is substantially the same as the background noise, and the noise of the first microphone is simplified. And the reduction amount is estimated only by the ratio of background noise. Noise (background noise) at the point of the first microphone 2 is averaged by the first averaging means 6a when the blower 51 which is a noise source is not driven, and the output signal thereof is
It is stored in the storage means 7a. Next, the noise at the point of the first microphone 2 when the blower 51, which is a noise source, is driven is averaged by the first averaging means 6a and input to the first dividing means 8a. In the first dividing means 8a, the first
The noise level-to-background noise level ratio at the microphone 2 point is calculated. The output signal of the first division means 8a is input to the first reduction amount calculation means 9a. First reduction amount calculation means 9
In a, first, the coherence γ ² is calculated from the equation (1-3).

[0040]

[Equation 2]

Next, the estimated reduction amount ΔSPL is calculated by the equation (1-2) or the simplified equation (1-4) from the calculated value of the equation (1-3). ΔSPL = 10 × Log (S ₁ / N ₁ ) −3 [dB] ... (Equation 1-4) Operation value of (Equation 1-2) or (Equation 1-4), that is, first reduction amount operation The output value (signal) of the means 9a is input to the first comparing means 10, and the first comparing means 10 causes the first level setting means 11 to reduce a certain noise amount-for example, a limit sound recognizable by humans. If the set value is lower than the first level setting means 11, the set value is set to a value of 3 dB that is a pressure level difference to a value of 5 dB that is a sound pressure level difference that can be clearly recognized by humans. The output signal of the comparison means 10 of 1 operates the stop means 12 in the active noise reduction device,
The operation of the active noise reduction device is stopped to suppress wasteful power consumption and abnormal noise due to unstable operation. Since the operating states of the blower 51 and the active noise reduction device are the same as those in FIG. 2 shown in the first embodiment, the description thereof will be omitted. In the present invention, the circuit scale is halved as compared with the case of the first embodiment.

Example 13 It should be noted that FIG.
In the above, the noise-to-background noise ratio on the first microphone 2 side is used, but the second microphone 3 side may be used. However, the detection of the noise level when the active noise reduction device is in operation is performed by suspending the operation of the active noise reduction device for a certain period of time.

Example 14 FIG. 6 is a diagram showing a system of an active noise reduction device according to a fifth embodiment of the present invention. In the air conditioning system shown in the figure, a blower 51, a heat exchanger 52, a compressor unit 53, an air conditioning system centralized control device 54, a sound absorbing material 55, and an active noise reduction device
Since the microphone 2, the second microphone 3, the muffler speaker 4, and the control circuit 5 have the same configuration and operation as those of the conventional example, the description thereof will be omitted and the components related to the present invention will be described in detail. A first averaging means 6a for averaging an output signal (sound pressure converted into an electric signal) of a first microphone provided for detecting a propagating sound wave from a blower 51 which is a noise source, and a noise source A first storage means 7a for averaging the noise (background noise) at the point of the first microphone 2 when is not driven by the first averaging means 6a and storing the output signal thereof. Wind speed (air volume) detection means 15 provided to detect the wind speed (air volume) in the sound wave propagation passage when the blower 51, which is a noise source, is driven.
And the wind speed (noise) -electric conversion averaging means 16 for converting and averaging into an electric signal corresponding to the output signal of the wind speed (air volume) detecting means 15, the output signal of the first storing means 7a and the wind speed (noise). ) -The first division means 8a for generating a division signal with the output signal of the electric conversion averaging means 16 is provided, and the first division means 8a
Second reduction amount calculation means 9b for calculating the estimated noise reduction amount by the output signal of the division means 8a, the output signal of the second reduction amount calculation means 9b, and the first level setting means 11
First, comparing with a set value corresponding to a certain noise reduction amount
The comparison means 10 and the stop means 12 that receives the output of the first comparison means 10 and stops the operation of the active noise reduction device are provided.

For the blower noise, the relation of (Equation 1-5) is obtained when the type of blower, the air volume and the total pressure are given. dB = dB _S +10 log ₁₀ (Q × P _t ² ) = dB _S +10 log ₁₀ (A × v × P _t ² ) ... (Equation 1-5) dB _S ...... Specific noise (typical noise characteristics of similar blower Value) Example of size Airfoil = 30 to 35 Multi-blade = 40 to 45 Axial flow = 50 to 55 Q ... Air volume [m ³ / s] Q = Cross sectional area A [m ² ] x wind speed v [m / s] P _t ...... total pressure [mmAq]

Next, the operation of the present invention will be described. Although the same operation as in the case of the twelfth embodiment is performed, in the present invention, since the noise of the blower 51 can be estimated from the wind speed from (1-5 expression) as described above, the estimated noise from this wind speed is The noise-to-background noise ratio is calculated from the background noise generated by the first microphone 2 and the reduction amount is estimated.
The noise (background noise) at the point of the first microphone 2 is averaged by the first averaging means 6a when the blower 51 which is the noise source is not driven, and the output signal thereof is the first storage means. Store in 7a. Next, when the blower 51, which is a noise source, is driven, the wind speed (air volume) installed in the air conditioning duct
The wind speed (noise) -the output signal of the electric conversion averaging means 16 which detects the wind speed by the detecting means 15 and converts and averages the electric signal corresponding to the noise level estimated by (1-5 formula) -first division The noise-to-background noise ratio of this air conditioning system is calculated based on the input signal to the means 8a and the output signal of the first storage means 6a. The output signal of the first dividing means 8a is input to the second reduction amount calculating means 9b, the same calculation as that of the twelfth embodiment is performed, and the output thereof is input to the first comparing means 10 and the first comparing means 10 When the output of the second reduction amount calculation means 9b is smaller than the certain noise reduction amount (same as the value of the first embodiment) in the first level setting means 11, the active noise reduction device The stop means 12 in the inside is operated to stop the operation of the active noise reduction device so as to suppress the generation of abnormal noise due to useless power consumption and unstable operation. The calculation formula of the second calculation means 9b is the same as that of the twelfth embodiment, and the operation state of the blower 51 and the active noise reduction device shown in FIG. As compared with the case of the twelfth embodiment, by estimating the noise level by the wind speed of the blower 51 that is the noise source, it is possible to reduce the influence of the microphone noise due to wind or the like. Can be improved.

Example 15 FIG. 7 is a diagram showing a system of an active noise reduction device according to claim 6 in the embodiment 15 of the present invention. In the air conditioning system shown in the figure, a blower 51, a heat exchanger 52, a compressor unit 53, an air conditioning system centralized control device 54, a sound absorbing material 55, and an active noise reduction device
Since the microphone 2, the second microphone 3, the muffler speaker 4, and the control circuit 5 have the same configuration and operation as those of the conventional example, the description thereof will be omitted and the components related to the present invention will be described in detail. A first microphone 2 provided to detect a sound wave propagated from a blower 51, which is a noise source.
The noise at the point of the first averaging means 6a for averaging the output signal (sound pressure converted into an electric signal) and the first microphone 2 when the blower 51 as a noise source is not driven. (Background noise) is averaged by the first averaging means 6a, and a first storage means 7a for storing the output signal thereof is provided, and inside the sound wave propagation path when the blower 51, which is a noise source, is driven. A wind pressure detecting means 17 provided to detect the wind pressure, a wind pressure (noise) -electric conversion averaging means 18 for converting and averaging the signal of the wind pressure detecting means 17 into an electric signal corresponding to a noise level, The first division means 8a for generating a division signal of the output signal of the first storage means 7a and the output signal of the wind pressure (noise) -electric conversion averaging means 18, and the output signal of the first division means 8a, Second reduction amount for calculating the estimated noise reduction amount And calculation means 9b, and an output signal of the second reduction amount calculating means 9b, the first level setting means 1
No. 1 first comparison means 10 for comparing a set value corresponding to a certain noise reduction amount, and stop means 12 for stopping the operation of the active noise reduction device by receiving the output of the first comparison means 10.
Is provided.

Next, the operation of the present invention will be described. Although the same operation as in the case of the twelfth embodiment is performed, in the present invention, the noise of the blower 51 can be estimated from the wind pressure from (1-5 expression) as described above. The reduction amount is estimated by obtaining the noise-to-background noise ratio with the background noise from the first microphone. The noise (background noise) at the point of the first microphone 2 is averaged by the first averaging means 6a when the blower 51 which is the noise source is not driven, and the output signal thereof is the first storage means. Store in 7a. Next, when the blower 51, which is a noise source, is driven, the wind pressure (total pressure or static pressure) detecting means 17 installed in the air conditioning duct detects the wind pressure, and (1-5
Wind pressure (noise) -electric conversion averaging means 18 for converting and averaging into an electric signal corresponding to the noise level estimated by
Is input to the first dividing means 8a, and the noise-to-background noise ratio of this air conditioning system is calculated from the output signal of the first storing means 7a. The output signal of the first dividing means 8a is input to the second reduction amount calculating means 9b, the same calculation as that of the twelfth embodiment is performed, and the output is input to the first comparing means 10.
In the first comparing means 10, the first level setting means 11
Then, when the output of the second reduction amount calculation means 9b is smaller than a certain noise reduction amount (the same as the value of the first embodiment), the stop means 12 in the active noise reduction device is operated to activate the active noise reduction device. The operation of the noise reduction device is stopped to suppress wasteful power consumption and generation of abnormal sound due to unstable operation. The calculation formula of the second calculation means 9b is the same as that of the twelfth embodiment, and the operation state of the blower 51 and the active noise reduction device shown in FIG. As compared with the case of the twelfth embodiment, by estimating the noise level by the wind pressure of the blower 51 that is the noise source, the influence of microphone noise due to wind or the like can be reduced, so that the noise-to-background noise ratio detection accuracy can be improved. Can be improved.

Example 16 FIG. 8 is a diagram showing a system of the active noise reduction system according to claim 7 in the sixteenth embodiment of the present invention. In the air conditioning system shown in the figure, a blower 51, a heat exchanger 52, a compressor unit 53, an air conditioning system centralized control device 54, a sound absorbing material 55, and an active noise reduction device
Since the microphone 2, the second microphone 3, the muffler speaker 4, and the control circuit 5 have the same configuration and operation as those of the conventional example, the description thereof will be omitted and the components related to the present invention will be described in detail. A first microphone 2 provided to detect a sound wave propagated from a blower 51, which is a noise source.
The noise at the point of the first averaging means 6a for averaging the output signal (sound pressure converted into an electric signal) and the first microphone 2 when the blower 51 as a noise source is not driven. (Background noise) is averaged by the first averaging means 6a, and a first storage means 7a for storing the output signal thereof is provided, and the blower 5 is driven when the blower 51 as a noise source is driven.
Rotation speed detection means 19 provided to detect the rotation speed of 1
And a rotation speed (noise) -electric conversion averaging means 20 for converting and averaging the signal of the rotation speed detecting means 19 into an electric signal corresponding to a noise level, and an output signal and a rotation speed of the first storing means 7a. (Noise) -first division means 8a for generating a division signal with the output signal of the electrical conversion averaging means 20, and a second division means for calculating an estimated noise reduction amount by the output signal of the first division means 8a. Reduction amount calculation means 9b, output signal of the second reduction amount calculation means 9b, and first level setting means 1
No. 1 first comparison means 10 for comparing a set value corresponding to a certain noise reduction amount, and stop means 12 for stopping the operation of the active noise reduction device by receiving the output of the first comparison means 10.
Is provided.

The change in performance when the rotation speed of the blower is changed is as shown in (1-6 expression). Q ₂ = Q ₁ (n ₂ / n ₁ ) ... (Equation 1-6) P ₂ = P ₁ (n ₂ / n ₁ ) ² ... (Equation 1-6) Q ₂ ...... Rotation speed n Air amount at ₂ [m ³ / s] Q ₁ ... Air amount at rotational speed n ₁ [m ³ / s] P ₂ ... Pressure at rotational speed n ₂ [mmAq] P ₁ ... Pressure at rotational speed n ₁ [MmAq] n ₂ ... Rotational speed n ₂ [m / s] n ₁ ... Rotational speed n ₁ [m / s] Therefore, the blower noise is calculated from (1-5 formula) (1-6 formula) Q ₂ P ₂ ² = Q ₁ P ₁ (n ₂ / n ₁ ) ⁵ (Equation 1-7) Since noise is proportional to the fifth power of the rotation speed ratio from Equation (1-7), it is predictable.

Next, the operation of the present invention will be described. Although the same operation as in the case of the twelfth embodiment is performed, in the present invention, as described above, the noise of the blower 51 is caused by the rotation speed ratio (the reference rotation speed of the rotation speed ratio is set during the rated operation during the rated operation). It is possible to estimate the reduction amount by calculating the noise-to-background noise ratio from the estimated noise from the rotation speed ratio (rotational speed) and the background noise from the first microphone 2. is there. Noise (background noise) at the point of the first microphone 2 is averaged by the first averaging means 6a when the blower 51 that is a noise source is not driven,
The output signal is stored in the first storage means 7a. next,
When the blower 51, which is a noise source, is driven, the number of rotations is detected by the number-of-rotations detecting means 19 installed near the blower 51, and converted into an electrical signal corresponding to the noise level estimated by (1-7 formula). The output signal of the averaging rotation speed (noise) -electric conversion averaging means 20 is input to the first dividing means 8a, and the noise-to-background noise ratio of this air conditioning system is calculated by the output signal of the first storing means 7a. calculate. The output signal of the first division means 8a is input to the second reduction amount calculation means 9b,
The same calculation as in the twelfth embodiment is performed, and the output is input to the first comparing means 10, and the first comparing means 10 causes the first level setting means 11 to perform a certain noise reduction amount (value of the first embodiment). When the output of the first reduction amount calculating means 9a is smaller than that of the above), the stopping means 12 in the active noise reduction device is operated to stop the operation of the active noise reduction device, resulting in unnecessary power consumption. It is intended to suppress the generation of abnormal sound due to consumption or unstable operation. The arithmetic expression of the second arithmetic means 9b is the twelfth embodiment.
Further, the operation state of the blower 51 and the active noise reduction device shown in FIG. In comparison with the case of the twelfth embodiment, by estimating the noise level by the rotation speed of the blower 51 that is the noise source, it is possible to reduce the influence of the microphone noise due to wind or the like, so that the noise-to-background noise ratio detection accuracy is improved. Can be improved.

Example 17 In addition, the above Examples 14 to 16
In the above, the background noise level is detected from the first microphone 2 side, but it may be detected from the second microphone 3 side.

Example 18. In the sixteenth embodiment, the rotation speed detecting means 20 is detected from the rotating portion of the blower 51, but the rotation speed command (electrical) signal of the centralized air-conditioning control device 54 may be used.

Example 19 In addition, although each of the above Examples 1 to 18 is shown to be used alone, it may be a combination thereof.

[0054]

As described above, according to the active noise reduction device of claim 1 of the present invention, when the rotating machine such as the blower 51, which is a noise source, is operating at a low noise level, The ratio (noise-to-background noise ratio) of the noise level and the background noise level at the two microphones 2 and 3 is calculated, and the estimated reduction amount or coherence is calculated based on the ratio.
a and 9b respectively, and the estimated noise level has a certain reduction amount, for example, 3 to 5 dB (coherence is 0.
Since the operation of the active noise reduction device is stopped when it is less than 5 to 0.68), unnecessary control of the power consumption and disturbance noise outside the duct when noise reduction by the active noise reduction device is not required It is possible to obtain an active noise reduction device that can prevent abnormal noise from being generated due to the unstable operation of.

According to the second aspect of the active noise reduction device of the present invention, as means for detecting the background noise level and the noise level, filter means having a certain characteristic, for example, auditory correction characteristic (A characteristic etc.) ) Or an active noise control frequency range of 50 to 500 Hz is provided, a noise-to-background noise ratio with high detection accuracy can be obtained for the active noise reduction device.

According to the active noise reduction apparatus of the third aspect of the present invention, the averaging means is provided by switching the output signals of the first microphone 2 and the second microphone 3.
Since the dividing means is shared, the circuit can be simplified.

According to the active noise reduction device of claim 4 of the present invention, one of the first microphone 2 and the second microphone 3 is assumed to have a noise-to-background noise ratio, and one of them is used. Since the noise reduction amount is estimated by using only the value, it is possible to significantly reduce the number of circuits.

According to the active noise reduction device of claim 5 of the present invention, the noise level of the noise source is estimated by the wind speed of the blower without using the microphone, so the influence of noise due to wind or the like is reduced. Therefore, a noise-to-background noise ratio with high detection accuracy can be obtained.

Further, according to the active noise reduction apparatus of claim 6 of the present invention, the noise level of the noise source is estimated by the wind pressure of the blower without using the microphone, so the influence of noise due to wind or the like is reduced. Therefore, a noise-to-background noise ratio with high detection accuracy can be obtained.

According to the seventh aspect of the active noise reduction system of the present invention, the noise level of the noise source is estimated by the rotation speed of the blower without depending on the microphone. The noise-to-background noise ratio with high detection accuracy can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a system of an active noise reduction device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a time transition of a noise level of the blower and an operating state of the active noise reduction device in the first embodiment of the present invention.

FIG. 3 is a diagram showing a system of an active noise reduction device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a system of an active noise reduction device according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a system of an active noise reduction system according to a fourth embodiment of the present invention.

FIG. 6 is a diagram showing a system of an active noise reduction device according to a fifth embodiment of the present invention.

FIG. 7 is a diagram showing a system of an active noise reduction device according to claim 6 in embodiment 15 of the present invention.

FIG. 8 is a diagram showing a system of an active noise reduction device according to a seventh embodiment of the present invention.

FIG. 9 is a system diagram of a conventional active noise reduction device.

[Explanation of symbols]

 1 Air Conditioning Duct 2 First Microphone 3 Second Microphone 4 Mute Speaker 5 Control Circuit 6 Averaging Means 7 Storage Means 8 Dividing Means 9 Reduction Amount Calculating Means 10 Comparing Means 11 Level Setting Means 12 Operation of Active Noise Reduction Device Stopping means 13 Stopping means 13 Filtering means 14 Switching means 15 Wind speed (air volume) detecting means 16 Wind speed (noise) -electric conversion averaging means 17 Wind pressure detecting means 18 Wind pressure (noise) -electric conversion averaging means 19 Rotation speed detection means 20 Rotation Number (noise) -electric conversion averaging means 51 Blower 52 Heat exchanger 53 Compressor unit 54 Centralized control device for air conditioning system 55 Sound absorbing material

Claims (7)

[Claims] 1. A first microphone provided for detecting a sound wave propagating from a noise source in a sound wave propagation path, and a sound wave having an opposite phase and the same amplitude as the sound wave propagating from the noise source. A muffler speaker that radiates and muffles the propagating sound wave by the sound wave interference; a second microphone that detects a composite sound wave of the propagating sound wave from the noise source and the sound wave emitted from the muffling speaker; and the first microphone. The control circuit is configured to receive the output signal of the microphone, generate a signal having characteristics of the opposite phase and the same amplitude, and control the drive signal of the silence speaker so that the output signal of the second microphone becomes zero. In the active noise reduction device according to the first aspect, a first flattener for averaging an output signal (sound pressure converted into an electric signal) of a first microphone provided for detecting a propagating sound wave from the noise source. The equalizing means and the first storage means for averaging the noise (background noise) at the first microphone point when the noise source is not driven by the first averaging means and storing the output signal thereof. And averaging the noise when the noise source is driven by the first averaging means to generate a division signal of the output signal of the first averaging means and the output signal of the first storage means. An output signal of the second microphone (sound pressure converted into an electric signal), which is provided with a first division means and detects a composite sound wave of a sound wave propagating from the noise source and a sound wave emitted from the muffling speaker Second averaging means for averaging, and noise (background noise) at the second microphone point when the noise source is not driven is averaged by the second averaging means and the output signal is stored. The second storage means for storing the noise generated when the noise source is driven Note that the first averaging means includes second dividing means for averaging by the second averaging means to generate a division signal of the output signal of the second averaging means and the output signal of the second storage means. Means for calculating the estimated noise reduction amount based on the output signals of the means and the second dividing means, and a certain noise of the output signal of the first reduction amount calculating means and the first level setting means. Active noise, characterized by comprising first comparing means for comparing a set value corresponding to the amount of reduction, and stop means for stopping the operation of the active noise reduction device in response to the output of the first comparing means. Reduction device. 2. A first microphone provided for detecting a sound wave propagating from a noise source in a sound wave propagation path, and a sound wave having an opposite phase and the same amplitude as the sound wave propagating from the noise source. A muffler speaker that radiates and muffles the propagating sound wave by the sound wave interference; a second microphone that detects a composite sound wave of the propagating sound wave from the noise source and the sound wave emitted from the muffling speaker; and the first microphone. The control circuit is configured to receive the output signal of the microphone, generate a signal having characteristics of the opposite phase and the same amplitude, and control the drive signal of the silence speaker so that the output signal of the second microphone becomes zero. In the active noise reduction device according to the first aspect, a first microphone provided for detecting a propagating sound wave from the noise source has an output signal (sound pressure converted into an electric signal) having a certain characteristic. The first averaging means for inputting to the first filter means to average the output of the first filter means and the noise (background noise) at the first microphone point when the noise source is not driven. The first averaging means is provided for averaging and the output signal thereof is stored, and the noise when the noise source is driven is averaged by the first averaging means to obtain the first averaging means. Of the averaging means and the output signal of the first storing means, the first dividing means for generating a divided signal, and the sound wave propagated from the noise source and the sound wave emitted from the muffling speaker are combined. A second microphone which inputs an output signal (sound pressure converted into an electric signal) of a second microphone for detecting a sound wave into a second filter means having a certain characteristic, and averages an output of the second filter means. If the averaging means and the noise source are not driving The second averaging means averages the noise (dark noise) at the second microphone point and stores the output signal of the second averaging means. The second averaging means is provided for averaging to generate a division signal of the output signal of the second averaging means and the output signal of the second storage means. A first noise reduction amount calculating unit that calculates an estimated noise reduction amount based on an output signal of the second dividing unit, and a noise reduction amount of the output signal of the first noise reduction amount calculating unit and the first level setting unit. The active noise reduction device is provided with first comparison means for comparing the set value corresponding to the above and stop means for stopping the operation of the active noise reduction device in response to the output of the first comparison means. . 3. A first microphone provided for detecting a sound wave propagating from a noise source in a sound wave propagation path, and a sound wave having an opposite phase and the same amplitude as the sound wave propagating from the noise source. A muffler speaker that radiates and muffles the propagating sound wave by the sound wave interference; a second microphone that detects a composite sound wave of the propagating sound wave from the noise source and the sound wave emitted from the muffling speaker; and the first microphone. The control circuit is configured to receive the output signal of the microphone, generate a signal having characteristics of the opposite phase and the same amplitude, and control the drive signal of the silence speaker so that the output signal of the second microphone becomes zero. In the active noise reduction device, the first microphone provided for detecting the sound wave propagating from the noise source, the sound wave propagating from the noise source, and the sound wave radiated from the muffling speaker are combined. First switching means for switching an output signal (sound pressure converted into an electric signal) with a second microphone for detecting an acoustic wave, and a first switching means for averaging the output signal of the first or second microphone. Averaging means and noise averaging the noise (background noise) at the first or second microphone point when the noise source is not driven by the first averaging means and storing output signals thereof Second switching means for switching the outputs of the first storage means and the second storage means, and an output signal of the first storage means or the second storage means and a second storage means. First division means for generating a division signal with the output signal of the first averaging means, output signal of the first storage means (background noise at the first microphone point), and output of the first averaging means The signal (the noise of the first microphone) and the calculated force signal are recorded. And a third storage means for storing the output signal of the ratio of the noise of the second microphone to the background noise calculated by the first dividing means and the third storage means (the noise of the first microphone and the background noise). (Divided value)
Output signal of the first reduction amount calculation means for calculating an estimated noise reduction amount, an output signal of the first reduction amount calculation means, and a set value corresponding to a certain noise reduction amount of the first level setting means. An active noise reduction device comprising: a first comparison device for comparing the above and a stop device for stopping the operation of the active noise reduction device in response to the output of the first comparison device. 4. A first microphone provided to detect a sound wave propagating from a noise source in a sound wave propagation path, and a sound wave having an opposite phase and the same amplitude as the sound wave propagating from the noise source. A muffler speaker that radiates and muffles the propagating sound wave by the sound wave interference; a second microphone that detects a composite sound wave of the propagating sound wave from the noise source and the sound wave emitted from the muffling speaker; and the first microphone. The control circuit is configured to receive the output signal of the microphone, generate a signal having characteristics of the opposite phase and the same amplitude, and control the drive signal of the silence speaker so that the output signal of the second microphone becomes zero. In the active noise reduction device, a first microphone (or a sound wave propagating from the noise source and a sound wave radiated from the muffling speaker) provided to detect the sound wave propagating from the noise source. And a first averaging means for averaging the output signal (sound pressure converted into an electric signal) of the second microphone for detecting the synthesized sound wave of Or (2) the noise (background noise) at the microphone point is averaged by the first averaging means,
A first storage unit that stores the output signal is provided, and noise generated when a noise source is driven is averaged by the first averaging unit, and the output signal of the first averaging unit and the first storage unit. A first division means for generating a division signal with the output signal of the means, and second reduction amount calculation means for calculating an estimated noise reduction amount by the output signal of the first division means; and the second reduction amount calculation means. The output signal of the reduction amount calculation means and the first level setting means,
It is characterized in that first comparison means for comparing a set value corresponding to a certain noise reduction amount and stop means for stopping the operation of the active noise reduction device in response to the output of the first comparison means are provided. Active noise reduction device. 5. A first microphone provided to detect a sound wave propagating from a noise source in a sound wave propagation path, and a sound wave having an opposite phase and the same amplitude as the sound wave propagating from the noise source. A muffler speaker that radiates and muffles the propagating sound wave by the sound wave interference; a second microphone that detects a composite sound wave of the propagating sound wave from the noise source and the sound wave emitted from the muffling speaker; and the first microphone. The control circuit is configured to receive the output signal of the microphone, generate a signal having characteristics of the opposite phase and the same amplitude, and control the drive signal of the silence speaker so that the output signal of the second microphone becomes zero. In the active noise reduction device according to the first aspect, a first flattener for averaging an output signal (sound pressure converted into an electric signal) of a first microphone provided for detecting a propagating sound wave from the noise source. The equalizing means and the first storage means for averaging the noise (background noise) at the first microphone point when the noise source is not driven by the first averaging means and storing the output signal thereof. A wind speed (air volume) detecting means provided to detect the wind speed (air volume) in the propagation path of the sound wave when a noise source is driven, and an electric signal corresponding to the output signal of the wind speed (air volume) detecting means. A wind speed (noise) to be converted and averaged into a signal-electric conversion averaging means, and a division signal of an output signal of the first storage means and a wind speed (noise) -output signal of the electric conversion averaging means Second reduction amount calculating means for calculating an estimated noise reduction amount by the output signal of the first dividing means, an output signal of the second reduction amount calculating means, and a first level setting. The first of the means for comparing with a set value corresponding to a certain noise reduction amount And compare means, said first active noise reduction apparatus characterized in that a stop means for stopping the operation of the active noise reduction apparatus receives the output of the comparison means. 6. A first microphone provided for detecting a sound wave propagating from a noise source in a sound wave propagation path, and a sound wave having an opposite phase and the same amplitude as the sound wave propagating from the noise source. A muffler speaker that radiates and muffles the propagating sound wave by the sound wave interference; a second microphone that detects a composite sound wave of the propagating sound wave from the noise source and the sound wave emitted from the muffling speaker; and the first microphone. The control circuit is configured to receive the output signal of the microphone, generate a signal having characteristics of the opposite phase and the same amplitude, and control the drive signal of the silence speaker so that the output signal of the second microphone becomes zero. In the active noise reduction device according to the first aspect, a first flattener for averaging an output signal (sound pressure converted into an electric signal) of a first microphone provided for detecting a propagating sound wave from the noise source. The equalizing means and the first storage means for averaging the noise (background noise) at the first microphone point when the noise source is not driven by the first averaging means and storing the output signal thereof. And a wind pressure detecting means provided for detecting the wind pressure in the propagation path of the sound wave when a noise source is driven, and a signal of the wind pressure detecting means is converted into an electric signal corresponding to a noise level and averaged. Wind pressure (noise) -electric conversion averaging means, first dividing means for generating a division signal of the output signal of the first storage means and wind pressure (noise) -electric conversion averaging means, The second noise reduction amount calculating unit that calculates the estimated noise reduction amount by the output signal of the first dividing unit, the output signal of the second noise reduction amount calculating unit, and the certain noise reduction amount of the first level setting unit. A first comparing means for comparing with a corresponding set value; Active noise reduction apparatus characterized in that a stop means for stopping the operation of the active noise reduction apparatus receives the output of the first comparison means. 7. A first microphone provided for detecting a sound wave propagating from a noise source in a sound wave propagation path, and a sound wave having an opposite phase and the same amplitude as the sound wave propagating from the noise source. A muffler speaker that radiates and muffles the propagating sound wave by the sound wave interference; a second microphone that detects a composite sound wave of the propagating sound wave from the noise source and the sound wave emitted from the muffling speaker; and the first microphone. The control circuit is configured to receive the output signal of the microphone, generate a signal having characteristics of the opposite phase and the same amplitude, and control the drive signal of the silence speaker so that the output signal of the second microphone becomes zero. In the active noise reduction device according to the first aspect, a first flattener for averaging an output signal (sound pressure converted into an electric signal) of a first microphone provided for detecting a propagating sound wave from the noise source. The equalizing means and the first storage means for averaging the noise (background noise) at the first microphone point when the noise source is not driven by the first averaging means and storing the output signal thereof. And a rotation speed detecting means provided for detecting the rotation speed of the rotating machine when the rotating machine which is a noise source is driven, and a signal of the rotation speed detecting means is converted into an electric signal corresponding to a noise level. First division for generating a division signal of the number of revolutions (noise) to be averaged-electric conversion averaging means, and the output signal of the first storage means and the number of revolutions (noise) -output signal of electric conversion averaging means Means and said first
Corresponding to a certain noise reduction amount of the second reduction amount calculation unit for calculating the estimated noise reduction amount by the output signal of the division unit, the output signal of the second reduction amount calculation unit, and the first level setting unit. An active noise reduction device comprising: first comparison means for comparing the set value to be set; and stop means for stopping the operation of the active noise reduction device in response to the output of the first comparison means.