JP2011079389A - Chattering noise prevention method and chattering noise prevention device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chattering noise prevention method and a chattering noise prevention device which prevent the generation of chattering noise in a cabin automatically. <P>SOLUTION: The chattering noise prevention method and device which prevent the generation of the chattering noise in a cabin by a low-pitched sound signal included in an audio signal, (1) reproduce a chattering test signal of a low frequency and emit the signal into a cabin from a speaker, and (2) collect the chattering noise generated in the cabin from a microphone provided in the cabin. Then, (3) a fluctuation signal which is caused by vibration which resonates with the low-frequency signal and amplitude-modulates the chattering noise signal is detected from the a sound signal collected by the microphone, and (4) a characteristic in the low-frequency of a frequency characteristic changing section (equalizer) into which the audio signal is input is controlled so that the fluctuation amount of the fluctuation signal reaches a set value or lower. By repeating the control about a plurality of low frequencies within a range of predetermined low frequencies, the generation of the chattering noise in a cabin is prevented. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a chatter noise generation prevention method and chatter noise generation prevention device, and more particularly to a chatter noise generation prevention method and chatter noise generation prevention device for preventing chatter noise from being generated in a vehicle interior due to a bass signal included in an audio signal. .

The chatter noise is an abnormal noise (noise) generated when a certain part of the vehicle interior resonates and parts touch each other when some vibration is applied to the vehicle. The present invention deals with chatter noise generated when a specific location in a vehicle interior resonates mainly with a signal reproduced in a low sound range when a general in-vehicle audio signal is reproduced with a certain output or more. FIG. 10 shows the state of occurrence of chattering sounds (billing, crumbling, rattling) in the passenger compartment.
As shown in FIG. 11, the chatter noise is generated by (a) a rain cover portion inside the driver's seat door trim, (b) a wire wiring portion inside the driver seat door trim, and (c) a glass rail portion inside the driver seat door iron plate. There are other parts equivalent to the parts (a) to (c). The chattering noise of the rain cover part (a) is generated as a hitting sound by striking the adjacent wiring wiring as a result of the separate piece structure (flap part) resonating greatly in the low frequency band of 50 Hz. The chatter noise of the wire wiring part in (b), when part of the wiring wiring inside the door is unwound and partially close to the iron plate surface, resonance increases in the 63 Hz band, and as a result, it is hit by contact. Occurs as sound. The chatter noise of the glass rail part in (c) interferes with the contact surface between the mechanism parts (rails) that move the door glass up and down and the door iron plate panel due to a large difference between the resonance points during 200 Hz playback. Is generated as a hitting sound.

It is necessary to prevent such chatter noise from occurring because it causes discomfort to the listener. For this reason, conventionally, every time the occurrence of chatter sound is detected by hearing, the occurrence location is empirically searched and specified based on how the chatter sound is generated or the direction of arrival of the sound, and predetermined measures are taken. For example, the chatter noise of the rain cover part in FIG. 11A is silenced by attaching a cushioning material (Epto sealer) to the lower end of the flap part and the wiring wiring after the occurrence location is specified. The chatter noise of the wire wiring portion in FIG. 11 (b) is silenced by bundling and attaching an ept sealer (sheet with double-sided tape) to the unwinding portion after identifying the occurrence location. The chatter noise of the glass rail part of (c) of FIG. 11 is silenced by identifying the place of occurrence, once removing the rail fixed to the door, reassembling, and filling the gap.
However, the above-described chatter noise generation suppression method is a method in which an operator searches and identifies a chatter noise occurrence location for each vehicle empirically and suppresses it manually, so experience and troublesome work are required. ing. Moreover, depending on the measure for suppressing chatter noise, the sound quality may change due to changes in the vehicle interior environment.

  As a prior art, a timbre evaluation apparatus that suitably evaluates a timbre in a vehicle has been proposed (Patent Document 1). According to this prior art, it is possible to evaluate the frequency and the magnitude of the chatter sound generated in the passenger compartment, but it does not specify the place where the chatter sound is generated, and the chatter sound is generated. Is not automatically prevented.

JP 2007-271485 A

In view of the above, an object of the present invention is to automatically prevent chatter noise in the passenger compartment.
Another object of the present invention is to prevent chatter noises in the passenger compartment and not affect the sound quality.

The present invention is a chatter noise generation prevention method and chatter noise generation prevention device for preventing chatter noise from being generated in a passenger compartment due to a bass signal included in an audio signal.
-Method for preventing chatter noise generation The method for preventing chatter noise generation according to the present invention includes a step of reproducing a low-frequency chatter test signal and releasing it from a speaker into the vehicle interior, and a chatter sound generated in the vehicle interior by a microphone provided in the vehicle interior. A step of collecting sound, a step of detecting from the microphone sound collection signal a fluctuation signal that is generated by vibration resonating with the low frequency signal and amplitude-modulates the chatter sound signal, and a fluctuation amount of the fluctuation signal is equal to or less than a set value. The step of controlling the characteristics at the low frequency of the frequency characteristic changing unit to which the audio signal is input, the step of repeating the above steps for a plurality of low frequencies within a predetermined low frequency range to prevent chatter noise from being generated in the vehicle interior ,have. In the step of controlling the gain, a plurality of chatter sound observation frequencies are set in advance, and a maximum fluctuation amount is detected among the low frequency fluctuation signals for amplitude-modulating the chatter sound signal of each observation frequency, The characteristic at the low frequency of the frequency characteristic changing unit is controlled so that the maximum fluctuation amount is not more than the set value.

The chatter sound generation prevention device of the present invention is generated in the vehicle interior by a chatter signal generation unit that reproduces a low frequency chatter test signal and emits it from the speaker to the vehicle interior, and a microphone provided in the vehicle interior. A chatter sound collecting unit that collects chatter sound, a fluctuation signal detecting unit that detects a fluctuation signal that amplitude-modulates the chatter sound signal caused by vibration that resonates with the low frequency signal, and an audio signal. An input frequency characteristic changing unit, and a characteristic control unit that controls the characteristic of the frequency characteristic changing unit at the low frequency so that a fluctuation amount of the fluctuation signal is equal to or less than a set value, and a plurality of frequency characteristic changing units within a predetermined low frequency range For each of the low frequencies, the low frequency characteristic of the frequency characteristic changing unit is controlled so that the fluctuation amount of the fluctuation signal is not more than the set value.
Further, the chatter sound generation prevention apparatus of the present invention sets a plurality of observation frequencies of the chatter sound in advance, and calculates the maximum fluctuation amount among the low frequency fluctuation signals for amplitude-modulating the chatter sound signal of each observation frequency. A maximum fluctuation amount detecting unit for detecting is provided, and the frequency characteristic control unit controls the characteristic at the low frequency of the frequency characteristic changing unit so that the maximum fluctuation amount is equal to or less than the set value.

According to the present invention, the low-frequency chatter test signal is reproduced and emitted from the speaker into the vehicle interior, and the chatter sound generated in the vehicle interior is collected by the microphone provided in the vehicle interior and resonates with the low-frequency signal. The frequency characteristic changing unit that detects the fluctuation signal that is caused by vibration and modulates the amplitude of the chatter sound signal from the microphone sound collection signal, and receives the audio signal so that the fluctuation amount of the fluctuation signal is equal to or less than a set value. Since the characteristics in frequency are controlled and the above steps are repeated for a plurality of low frequencies within a predetermined low frequency range, it is possible to prevent chatter noises in the passenger compartment. When controlling the characteristics at the low frequency of the frequency characteristic changing unit, a higher Q (10 or more) is set to the frequency band near the resonance point to affect the sound quality by reducing the narrow band characteristics. In other words, the influence on the audibility can be reduced.
In addition, according to the present invention, a plurality of chatter sound observation frequencies are set in advance, and the maximum fluctuation amount is detected among the low frequency fluctuation signals for amplitude-modulating the chatter sound signal of each observation frequency, and the maximum Since the characteristic at the low frequency, for example, the gain, of the frequency characteristic changing unit is controlled so that the fluctuation amount is equal to or less than the set value, the generated chatter sound can be accurately identified and muffled.

It is a schematic block diagram of the chatter sound generation prevention apparatus of this invention. It is explanatory drawing of the generation | occurrence | production mechanism of a chatter sound. It is a whole lineblock diagram of the chatter sound generation prevention device of the present invention. Equal loudness curve. It is a block diagram of a loudness calculating part. It is a block diagram of a frequency-limited loudness detection part. It is explanatory drawing of the fluctuation frequency fi and the observation frequency Fj. It is a chatter noise prevention processing flow. It is a detailed processing flow of step 105 of FIG. It is explanatory drawing of the chatter sound which generate | occur | produces in a vehicle interior. It is a generation | occurrence | production location and generation factor explanatory chart of a chatter sound.

(A) Outline of the Invention FIG. 1 is a schematic configuration diagram of a chatter noise prevention apparatus of the present invention. In order to suppress the occurrence of chatter noise, it is checked whether or not a vibration that causes chatter noise is generated by a predetermined low-frequency signal (bass signal). The low frequency characteristic (for example, gain) is controlled by a frequency characteristic changing unit (equalizer).
For this purpose, first, a chatter test signal having a predetermined low frequency is generated from the chatter test signal generator 11 of the audio apparatus 10, and the speaker is connected via a DSP frequency characteristic changing unit (for example, equalizer) 12 and an amplifier (AMP) 13. The reproduced sound having a frequency lower than −21 is emitted to the vehicle interior space 20. The microphone 22 provided near the driver's seat in the passenger compartment space collects chatter sounds generated in the passenger compartment due to the low sound and feeds back to the audio device 10. The collected signal is AD converted and input to the chatter sound generation prevention unit 14. The chatter sound generation prevention unit 14 checks whether or not vibration that causes chatter sound is generated from the collected sound signal, and if so, the predetermined low frequency characteristic of the equalizer 12 is reduced so that the vibration is reduced. Control. If such control is processed for all bass signals (for example, in increments of 5 Hz) within a predetermined low frequency range (for example, 20 Hz to 200 Hz) that causes chatter noise, it is possible to prevent chatter noise. In FIG. 1, reference numeral 15 denotes an audio source.

The chattering generation mechanism is because a member having a specific location in the vehicle interior that is resonated by a bass signal having a predetermined frequency vibrates and strikes another member. The frequency of chatter sounds that humans feel as an unusual sound is 1 KHz to 12.5 KHZ, which is higher than the vibration frequency. For this reason, the chatter sound is amplitude-modulated by vibration. That is, as shown in FIG. 2, the chatter signal 2 is amplitude-modulated by the vibration signal 1 having a resonance frequency (frequency of the bass signal), and the chatter noise increases as the vibration amplitude increases. Hereinafter, the vibration signal is referred to as a fluctuation signal, the resonance frequency is referred to as a fluctuation frequency, and the amplitude Av of the vibration signal is referred to as a fluctuation amount.
If the frequency of the chatter sound generated by vibration is known, it is easy to input a sound collection signal to a bandpass filter that passes the frequency signal component, and to detect the fluctuation signal by detecting the output signal. The fluctuation amount Av can be detected. However, the frequency of the chatter sound is unknown. Therefore, the chatter noise generation prevention unit 14 is provided with a band pass filter having each of a plurality of observed frequencies in the frequency range of 1 KHz to 12.5 KHZ as a pass center frequency, and a collected signal is transmitted to each band pass filter. Input, detect each band pass filter output signal to detect the fluctuation amount, and consider the observation frequency corresponding to the maximum fluctuation amount among the detected fluctuation amounts as the frequency of the chatter sound generated by the resonance vibration, The characteristic of the fluctuation frequency (resonance frequency) of the equalizer 12 is changed so as to decrease if the maximum fluctuation amount is larger than the set threshold value.

(B) Configuration of chattering sound generation preventing apparatus FIG. 3 is an overall configuration diagram of the chattering sound generation preventing apparatus of the present invention, and the same parts as those in FIG. A different point is that a detailed configuration of the chatter noise generation prevention unit 14 is shown.
The frequency range of the low frequency signal that generates chatter noise is 20 Hz to 200 Hz, and ₃₇ frequencies f ₁ = 20 Hz, f ₂ = 25 Hz,..., F ₃₇ = 200 Hz in 5 Hz increments within the frequency range. Are sequentially generated to suppress chatter noise, the chatter test signal generator 11 generates an i-th (i = 1 to 37) low-frequency fi chatter test signal, and a DSP characteristic frequency characteristic changer ( The reproduced sound having a frequency lower than that of the speaker 21 is emitted to the vehicle interior space 20 through the equalizer 12 and the analog signal amplifier (AMP) 13. The microphone 22 provided in the vicinity of the driver's seat in the passenger compartment space collects chatter sounds generated in the passenger compartment due to the low sound and inputs the collected chatter sounds to the chatter noise prevention unit 14.

  The loudness calculating unit 31 of the chattering noise generation preventing unit 14 adds an audible characteristic such as masking to the volume of sound as a physical quantity, and converts the volume into a volume of sound (loudness) that a human can actually hear. The sound characteristic of the human ear has the property that the low frequency range and wide frequency range cannot be heard, and is particularly noticeable at low volumes. The sound pressure level at each frequency that can be heard as a sound of the same magnitude on the basis of the sound pressure level of a pure tone of 1000 Hz is shown by an equal loudness curve shown in FIG. In FIG. 4, the lower curve corresponds to the case where the volume is lower, and the lower curve is the minimum audible limit, and it can be seen that the lower range and the higher range become harder to hear as the volume decreases. . Therefore, the loudness calculating unit 31 converts the input signal (billing sound signal) to low and high frequencies on the basis of an equal loudness curve corresponding to the sound volume, and converts it into a sound level actually heard by humans. FIG. 5 is a block diagram of the loudness calculation unit 31. A sound pressure level detection unit 31a for detecting the sound pressure level (volume) of the chatter sound signal, and a characteristic opposite to the equal loudness curve is stored as a loudness conversion characteristic according to the volume. A loudness conversion characteristic storage unit, and a loudness conversion unit 31c that converts an input signal (billing sound signal) into a volume of sound actually heard by a human using the loudness conversion characteristic according to the sound volume.

The frequency limit loudness detection unit 32 extracts a plurality of, for example, 12 frequencies within the chatter frequency range of 1 kHz to 12.5 KHZ as observation frequencies (F1 to F12), and extracts and outputs the frequency components of the observation frequencies. To do. Figure 6 is a block diagram of a frequency limiting loudness detector 32, a band-pass filter 32a ₁ ~32a ₁₂ and a predetermined band-pass filter output signal of the predetermined bandpass having a center frequency of each observation frequency (F1 to F12) A selector 32b for selecting and outputting is provided. That is, when the i-th (i = 1 to 37) low-frequency fi chatter test signal is output from the chatter-test signal generator 11, the band-pass filters 32 a _{1 to} 32 a ₁₂ receive low-frequency signals including the low-frequency fi. enter sequentially at a predetermined timing to the amplitude-modulated wave component detecting section 33 _to 333 ₃₇ via the selector 32b extracts the signal (amplitude modulation signal) of the amplitude-modulated by observation frequency Fj (j = 1 to 12). The observation frequencies F1 to F12 are assumed to be 1000 Hz, 1250 Hz, 1600 Hz, 2000 Hz, 2500 Hz, 3150 Hz, 4000 Hz, 5000 Hz, 6300 Hz, 8000 Hz, 10000 Hz, and 12,500 Hz as shown on the horizontal axis of FIG.

As shown on the vertical axis of FIG. 7, each amplitude modulation wave component detection unit 33 _{1 to} 33 ₃₇ has 5 Hz within the low frequency range when the frequency range of the low frequency signal that generates chatter noise is 20 Hz to 200 Hz. It is provided for each step frequency f ₁ = 20 Hz, f ₂ = 25 Hz,..., F ₃₇ = 200 Hz, and is composed of a fluctuation component extraction filter that handles a band having these as center frequencies. In other words, by extracting (1) if chatter test signal frequency 20Hz is output, variation signal fluctuation frequency 20Hz than the respective amplitude-modulated wave component detecting unit 33 ₁ 12 of the amplitude modulation signal (see FIG. 2) When input to the next-stage modulated wave component maximum value detection unit 34 and (2) a chatter test signal with a frequency of 25 Hz is output, the amplitude modulation wave component detection unit 33 ₂ has a variable frequency from each of the 12 amplitude modulation signals. When a 25 Hz fluctuation signal is extracted and input to the modulation wave component maximum value detection unit 34, and similarly, (3) when a chatter test signal having a frequency of 200 Hz is output, 12 amplitude modulation wave component detection units ₃₃₃₇ are provided. A fluctuation signal having a fluctuation frequency of 200 Hz is extracted from each of the amplitude modulation signals and input to the modulation wave component maximum value detection unit.

When variation signal of the modulating wave component maximum value detector 34 12 variation frequency fi is input from a predetermined amplitude-modulated wave component detecting section 33 _to 333 _37, the amount of fluctuation detects the maximum variation signal, said maximum variation The amount is input to the frequency characteristic control unit 35. The frequency characteristic control unit 35 checks whether or not the maximum fluctuation amount is larger than the set threshold value, and if so, the equalizer so as to lower the gain of the fluctuation signal frequency (fluctuation frequency) fi by a predetermined amount so that the maximum fluctuation amount becomes smaller than the set threshold value. 12 characteristics are controlled. Since the equalizer 12 is composed of a DSP (digital signal processor) and the gain can be controlled in increments of a predetermined frequency, it will not be described in detail. When controlling the gain, setting Q to 10 makes it possible to narrow the bandwidth for decreasing the gain, and to prevent deterioration in sound quality when an audio signal is input.

(C) Chatter sound generation prevention process FIG. 8 is a chatter sound generation prevention process flow. The outline of the process is as follows. (1) The frequency range of the low frequency signal that generates the chatter sound is 20 Hz to 200 Hz. Generates a chatter test signal having the i-th frequency fi among ₃₇ frequencies f ₁ = 20 Hz, f ₂ = 25 Hz, ..., f ₃₇ = 200 Hz in increments of 5 Hz, and (2) a chatter test signal of the frequency fi Check whether the fluctuation amount Av (Fig. 2) of the fluctuation signal that causes chatter noise is larger than the set value from the collected sound signal when the sound is generated, and control the equalizer characteristics so that the fluctuation amount Av becomes smaller if it is larger Then, such control is performed for all 37 frequencies to prevent chatter noise.
First, i is set to 1 (step 101), and then it is checked whether i <38, in other words, processing has been completed for all 37 frequencies (step 102). If i ≧ 38, the processing is terminated. To do. However, if i <38, the test chatter signal of the i-th frequency fi is generated from the chatter test signal generator 11 and the reproduced sound is output from the speaker 21 via the equalizer 12 and the analog signal amplifier 13. 20 (step 103). The volume is adjusted so that the vehicle interior sound pressure level is 70 to 75 dBSPL.

The microphone 22 provided in the vicinity of the driver's seat in the passenger compartment collects chatter sounds generated in the passenger compartment by the reproduced sound and inputs them to the chatter noise prevention unit 14 (step 104). When the collected sound signal is input, the chattering noise generation prevention unit 14 performs the fluctuation sound analysis to calculate the fluctuation amount xi (step 105). That is, the frequency limit loudness detection unit 32 of the chatter noise generation prevention unit 14 sequentially extracts and outputs the frequency components (amplitude modulation signals) of the observation frequencies F1 to F12, and the i-th amplitude modulation wave component detection unit 33 _i A fluctuation signal having a fluctuation frequency fi is extracted from each of the twelve amplitude modulation signals and input to the next-stage modulation wave component maximum value detection unit 34. The modulation wave component maximum value detection unit 34 detects a fluctuation signal having the largest fluctuation amount when the fluctuation signals of twelve fluctuation frequencies fi are input, and inputs the maximum fluctuation amount xi to the frequency characteristic control unit 35.

The frequency characteristic control unit 35 checks whether the maximum fluctuation amount xi is larger than a set threshold value (for example, 100 mDLF) (step 106), and if so, decreases the gain of the fluctuation frequency fi by a predetermined amount so that the maximum fluctuation amount becomes smaller than the set threshold value. Next, the characteristic of the equalizer 12 is controlled (step 107). DLF is an abbreviation for Depth of Loudness Fluctuation, and is the depth (peak-to-peak) of the time-varying mountain valley of the loudness. It is an empirical value that when the fluctuation amount becomes 100 mDLF or less, the chatter sound is subdued and heard.
Thereafter, the process returns to step 103, and the subsequent processing is performed until the maximum fluctuation amount becomes smaller than the set threshold value. In step 106, if the maximum fluctuation amount xi is equal to or smaller than the set threshold value, i is incremented (i + 1 = i, step 108), and the processes in and after step 102 are repeated.
As described above, the chatter sound generated by the low sound within the frequency range becomes equal to or less than the set threshold value, and the chatter sound is subsided.

FIG. 9 is a detailed process flow of step 105. As shown in FIG. 7, i = 1 to 37, and fi (Hz) is the frequency (fluctuation frequency) of the i-th chatter test signal, and j = 1 to 12, and Fj (Hz ) Is the jth observation frequency.
Let Pi be the sound pressure observed by the microphone 22 when the i-th chatter test signal is reproduced. A control unit (not shown) for controlling the chatter noise generation prevention unit 14 is set to j = 1 (step 201), and the loudness calculation unit 31 to the frequency limit loudness detection unit 32 are used for the band of the observation frequency Fj (Hz). The loudness value Loud (Pi) detected in (1) is measured (step 202).
Next, when the fluctuation amount of the fluctuation frequency fi (Hz) at the observation frequency Fj (Hz) is xij (mDLF), the i-th amplitude modulation wave component detection unit 33 _i uses the fi (Hz) as a center frequency. (Bandpass pass filter) is used to calculate the variation xij (mDLF)
xij ＝ BPF (Loud (Pi) j) i
Is obtained and input to the modulation wave component maximum value detection unit 34, and the modulation wave component maximum value detection unit 34 stores xij (step 204). The control unit checks whether j = 12 (step 205). If j <12, j is incremented (j + 1 = j, step 206), and the processing from step 202 onward is repeated.
On the other hand, if j = 12, the modulation wave component maximum value detection unit 34 detects the maximum fluctuation amount xi among the twelve fluctuation amounts, and inputs the maximum fluctuation amount xi to the frequency characteristic control unit 35 (step S1). 307).

In the above description, an example in which an amplitude modulation wave component extraction unit is provided for each frequency f ₁ = 20 Hz, f ₂ = 25 Hz,..., F _n = 200 Hz in the range of the low frequency 20 Hz to 200 Hz is shown. However, the present invention is not limited to these numerical values. Moreover, although the example of F1-F12 was shown as an observation frequency, this invention is not limited to these numbers and frequencies in an Example similarly.
Further, in the configuration of FIG. 3, an amplitude modulation wave component extraction unit is provided for each frequency f ₁ = 20 Hz, f ₂ = 25 Hz,..., F _n = 200 Hz in the range of low frequency 20 Hz to 200 Hz. Although the detection accuracy is slightly lowered, a simple configuration in which one fluctuation component extraction filter having a pass band of 20 Hz to 200 Hz is also possible. Moreover, although the block diagram when the chattering noise generation prevention unit 14 is configured by hardware is shown, it can also be configured by software by a microcomputer.

DESCRIPTION OF SYMBOLS 10 Audio apparatus 11 Chatter test signal generation part 12 Frequency characteristic change part (for example, equalizer)
13 Amplifier (AMP)
14 chatter noise prevention unit 15 audio source 20 vehicle interior space 21 speaker 22 microphone

Claims (4)

In a chatter noise prevention method for preventing chatter noise from being generated in a passenger compartment due to a bass signal included in an audio signal,
Regenerating a low-frequency chatter test signal and releasing it from the speaker into the passenger compartment;
A step of collecting chatter sounds generated in the vehicle interior by a microphone provided in the vehicle interior;
Detecting a fluctuation signal generated by vibration resonating with the low-frequency signal and amplitude-modulating a chatter sound signal from the microphone sound collection signal;
Controlling the characteristic at the low frequency of the frequency characteristic changing unit to which the audio signal is input so that the fluctuation amount of the fluctuation signal is equal to or less than a set value;
Repeating the above steps for a plurality of low frequencies within a predetermined low frequency range to prevent chatter noises from being generated in the passenger compartment.
A method for preventing chatter noise generation. A plurality of observation frequencies of the chatter sound are set in advance, and the maximum fluctuation amount is detected among the low frequency fluctuation signals for amplitude-modulating the chatter sound signal of each observation frequency,
Controlling the characteristics at the low frequency of the frequency characteristic changing unit so that the maximum fluctuation amount is equal to or less than the set value;
The method for preventing chatter noise generation according to claim 1. In a chatter noise prevention device for preventing chatter noise from being generated in a passenger compartment due to a bass signal included in an audio signal,
A chatter signal generator that plays back a low-frequency chatter signal and emits it from the speaker into the passenger compartment.
A chatter sound collecting unit that collects chatter sounds generated in the vehicle interior by a microphone provided in the vehicle interior,
A fluctuation signal detection unit that detects a fluctuation signal that is generated by vibration resonating with the low-frequency signal and amplitude-modulates a chatter sound signal from the microphone sound collection signal;
Frequency characteristic changing part to which an audio signal is input,
A characteristic control unit for controlling a characteristic at the low frequency of the frequency characteristic changing unit so that a fluctuation amount of the fluctuation signal is equal to or less than a set value;
And for each of a plurality of low frequencies within a predetermined low frequency range, each low frequency characteristic of the frequency characteristic changing unit is controlled so that a fluctuation amount of a fluctuation signal is equal to or less than the set value. A chatter noise prevention device. A maximum fluctuation amount detection unit that sets a plurality of observation frequencies of the chatter sound in advance and detects a maximum fluctuation amount among the low frequency fluctuation signals that amplitude-modulate the chatter sound signal of each observation frequency;
The characteristic correction unit controls the characteristic at the low frequency of the frequency characteristic changing unit so that the maximum fluctuation amount is equal to or less than the set value.
The chatter noise prevention apparatus of Claim 3 characterized by the above-mentioned.

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