JPH0766651A - Audio device - Google Patents

Abstract

PURPOSE:To perform an auto equalizing by determining the frequency characteristic of an equalizer so as to be a desired overall frequency characteristic even if white noise is not generated. CONSTITUTION:A microphone 14c detects sound in acoustic space and an adaptive signal processing part 19 executes an adaptive signal processing and outputs the audio signal component yn of the low-pass in an observation point by using the low-pass component Sd' of a detection signal and the low-pass component xn of an audio signal to be inputted as a reference signal. An arithmetic part 22 synthesizes the high-pass component of the audio signal contained in a detection signal Sd and the low-pass component of the audio signal in the observation point and outputs an audio signal Sa2 in the observation point. A controller 23 determines the level in each frequency zone of an audio signal Sa1 to be outputted from an audio source and the audio signal Sa2 in the observation point and determines the frequency characteristic of an equalizer so that an overall frequency characteristic may be a prescribed frequency characteristic based on the level of each zone of the both signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio device, and more particularly, it automatically sets the frequency characteristic of an equalizer so that the total frequency characteristic becomes a desired characteristic, and also based on the level of each frequency band of noise. Noise is masked by adjusting the frequency characteristics of the equalizer.
The present invention relates to an audio device that automatically sets a volume based on a noise level.

[0002]

2. Description of the Related Art An audio device has a function called an auto equalizer. This is because a predetermined frequency characteristic is stored in a memory in advance, and the frequency characteristic is set to the equalizer by operating the auto equalizer key so that the overall frequency characteristic including the acoustic space is controlled to be a desired characteristic. It is a function.

In order to realize this auto equalizer function, it is necessary to grasp the frequency characteristic of the acoustic space where the audio sound is emitted from the speaker. FIG. 6 is a main part configuration diagram of an audio device that realizes a conventional auto equalizer function. In the figure, reference numeral 1 denotes an equalizer, which is a bandpass filter network 1a for outputting each frequency band component of an audio signal Sa output from an audio source (not shown) and a gain corresponding to each band component according to a predetermined frequency characteristic. It has a variable gain amplifier 1b ₁ ~1bn for multiplying, a combining unit 1c for combining the gain-variable amplifier output. Two
Is a noise oscillator used for measuring the frequency characteristic of the acoustic space, and is configured to generate white noise having a flat level over the entire area, for example. 3 is a switch for selecting the equalizer output and the noise oscillator output, 4 is a power amplifier, and 5 is an acoustic space such as a vehicle interior space.

The acoustic space 5 is provided at an observation point such as a speaker 5a that radiates an audio sound, an audio sound propagation system 5b, and the vicinity of the listener's ear, and a microphone 5c that detects the audio sound radiated and propagated from the speaker. Composed of. 6 is a band pass filter network that outputs each frequency band component of the audio signal at the observation point detected by the microphone, 7 is the level (amplitude) of each frequency band of the audio signal at the observation point, and the total frequency characteristic is The gain in each frequency band of the equalizer is determined so as to have a desired characteristic (for example, a flat characteristic), and the gain is stored in a built-in memory. When the auto equalizer function is requested, the gain is adjusted in each gain variable amplifier in the equalizer 1. a frequency characteristic analyzing unit for setting to 1b ₁ ~1bn.

To determine the gain set in the equalizer by the auto equalizer function, the output of the noise oscillator 2 is selected by the switch 3 and white noise is output from the speaker 5a. The microphone 5c detects white noise radiated from the speaker and propagates, and inputs it to the bandpass filter 6. The bandpass filter 6 separates the white noise at the observation point input from the microphone for each frequency band and inputs the white noise to the frequency characteristic analysis unit 7. Frequency characteristic analyzing unit 7 Overall frequency characteristics are stored in the memory to determine the gain of the desired variable gain amplifier 1b ₁ ~1bn so that the frequency characteristics based on the signal level in each frequency band. After that, the switch 3 selects the equalizer output. When the auto equalizer function is not required, the gain set by the equalizer characteristic setting unit (not shown) is input to the variable gain amplifiers 1b _{1 to} 1bn to control the frequency characteristic, but the auto equalizer function is required. and a gain that is stored in the memory by entering into the gain variable amplifier 1b ₁ ~1bn to the desired properties of the overall frequency characteristics.

[0006]

However, in the conventional method for realizing the auto equalizer, it is necessary to output a flat noise to the acoustic space over the entire area, which is uncomfortable for the user. Further, in the conventional method, there is a problem that music cannot be heard when the gain is determined so as to obtain a desired total frequency characteristic. Further, in the conventional method, if the gain is determined during running, the measurement accuracy is lowered, and there is a problem that a desired total frequency characteristic cannot be obtained. this is,
This is because road noise, engine sound, etc. are generated in the passenger compartment while the vehicle is running, and thus the signal detected by the microphone contains road noise and engine sound in addition to white noise.

From the above, the object of the present invention is to obtain the frequency characteristic (gain of each band) of the equalizer which gives a desired total frequency characteristic without generating white noise, and moreover, while driving. It is an object of the present invention to provide an audio device capable of adjusting the frequency characteristic of an equalizer so that a desired total frequency characteristic can be obtained even while listening to music. It is another object of the present invention to provide an audio device capable of masking noise by adjusting the frequency characteristic of the equalizer based on the noise level in a plurality of frequency bands. Still another object of the present invention is to provide an audio device capable of automatically setting the volume based on the noise level.

[0008]

A problem relating to the above-mentioned auto equalizer is that a detection unit for detecting a sound at a predetermined observation point in an acoustic space and a low frequency component of a detection signal output from the detection unit are input. At the same time, a low-frequency component of the audio signal is input as a reference signal, and an adaptive signal processing unit that performs adaptive signal processing so as to cancel the low-frequency audio signal component included in the detection signal, and an audio included in the detection signal An audio signal output unit that combines the high-frequency component of the signal and the low-frequency component of the audio signal at the observation point output from the adaptive signal processing unit to output the audio signal at the observation point, and the audio signal output from the audio source Obtain the levels of the audio signal in multiple frequency bands at the observation point and use the levels of both signals in each frequency band as the basis. There are, overall frequency characteristics including equalizer and acoustic space is achieved by a frequency characteristic determining unit for determining a frequency characteristic of the equalizer so as to have a predetermined frequency characteristic.

Further, a problem related to the masking correction is that a detection unit for detecting a sound at a predetermined observation point in an acoustic space, a low frequency component of a detection signal output from the detection unit, and an audio signal are input. The low-frequency component of is input as a reference signal, and an adaptive signal processing unit that performs adaptive signal processing so as to cancel the low-frequency audio signal component included in the detection signal, and an observation point output from the adaptive signal processing unit A noise signal output unit that outputs a noise signal by subtracting the low-frequency component of the audio signal from the low-frequency component of the detection signal, and the level of the noise signal in a plurality of frequency bands is detected. The higher the level, the higher the gain. This is achieved by the frequency characteristic correction unit that corrects the frequency characteristic of the equalizer.

Further, a problem related to the above-mentioned auto volume is that a detection unit for detecting a sound at a predetermined observation point in an acoustic space and a low frequency component of a detection signal output from the detection unit are input and an audio signal is detected. The low-frequency component of is input as a reference signal, and an adaptive signal processing unit that performs adaptive signal processing so as to cancel the low-frequency audio signal component included in the detection signal, and an observation point output from the adaptive signal processing unit This is achieved by a noise signal output unit that outputs a noise signal by subtracting the low frequency component of the audio signal from the low frequency component of the detection signal, and a volume control unit that controls the volume based on the level of the noise signal.

[0011]

A detection unit such as a microphone detects a sound at a predetermined observation point in an acoustic space, and an adaptive signal processing unit detects a low frequency component of the detection signal and a low frequency component of an audio signal input as a reference signal. Adaptive signal processing is performed using the output signal and an audio signal component in the low frequency band is output from the adaptive filter. The audio signal output unit combines the high frequency component of the audio signal included in the detection signal and the low frequency component of the audio signal at the observation point output from the adaptive signal processing unit (adaptive filter), and outputs the audio signal at the observation point. . The frequency characteristic setting unit obtains levels in a plurality of frequency bands of the audio signal output from the audio source and the audio signal at the observation point, and based on the levels in each frequency band of both signals, the total frequency characteristic is a predetermined frequency characteristic. The frequency characteristic of the equalizer is determined so that By doing so, the frequency characteristic of the equalizer (gain of each band) can be obtained so as to obtain a desired total frequency characteristic without generating white noise, and further, even while running, The frequency characteristic of the equalizer can be obtained so that the desired total frequency characteristic can be obtained even while listening to music.

The noise signal output section subtracts the low-frequency component (adaptive filter output) of the audio signal from the low-frequency component of the detection signal and outputs the noise signal at the observation point. The level of the noise signal in the band is detected, and the frequency characteristic of the equalizer is corrected so that the gain increases as the level increases. This enables masking correction according to the noise level. Furthermore, the volume control unit can control the volume based on the noise level, so that the volume can be increased and the music can be listened to even if the noise level increases.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Overall Configuration FIG. 1 is an overall configuration diagram of an audio device of the present invention.
Reference numeral 11 denotes an equalizer, which corresponds to a filter bank 11a including a bandpass filter that outputs each frequency band component of an audio signal Sa output from an audio source (not shown), and each band component according to a predetermined frequency characteristic. gain multiplying a gain variable amplifier 11b ₁ ~11bn
And a combining unit 11c that combines the outputs of the variable gain amplifiers. 12 is an electronic volume for volume control, 13
Is a power amplifier, and 14 is an acoustic space such as a vehicle interior space. The acoustic space 14 is a speaker 1 that emits audio sound.
4a, an audio sound propagation system 14b, and a microphone 14c provided at an observation point in the vicinity of the listener's ear and detecting an audio sound radiated from a speaker and propagated.

Reference numeral 15 is a low-pass filter for outputting the low-frequency component of the audio signal Sa output from the audio source, which outputs the low-frequency component according to the frequency band of road noise or engine sound, and 16 and 17 are speakers. To a microphone, a delay characteristic adding unit for giving a signal delay characteristic, 18 is a low-pass filter for outputting a low-frequency component of a detection signal Sd (including an audio signal and noise at an observation point) detected by the microphone, and is a load noise It outputs the low frequency component according to the frequency band of the engine sound. 1
Reference numeral 9 denotes an adaptive signal processing unit, which is a low frequency component S of the detection signal Sd.
While d'is input, the low frequency component of the audio signal Sa is input as a reference signal, so that the low frequency audio signal component included in the detection signal Sd is canceled, in other words, the low frequency audio signal component yn. Is output based on the LMS (Least Mean Square) algorithm.

Reference numeral 20 is a detection signal S detected by the microphone.
It is a high-pass filter that outputs the high frequency component of d (including the audio signal and noise at the observation point), and outputs the high frequency component outside the frequency band of road noise and engine sound. Therefore, the high pass filter 20 outputs the high frequency component of the audio signal at the observation point. Reference numeral 21 denotes the output signal yn (low-frequency audio signal at the observation point) of the adaptive signal processing unit 19 based on the low-frequency component Sd '(including the low-frequency component and noise of the audio signal at the observation point) included in the detection signal Sd. Is output by subtracting the noise signal Sn, and 22 is a high-frequency component of the audio signal at the observation point and the output signal yn of the adaptive signal processing unit 19 (low-frequency audio signal at the observation point) is added to the observation point. An arithmetic unit for outputting the audio signal Sa ₂ in 23 is a controller for performing auto-equalizing, masking noise, and adjusting a volume according to the noise level.

Adaptive signal processing unit The adaptive signal processing unit 19 has an adaptive filter 19a having a digital filter configuration and an LMS signal processing unit 19b for performing adaptive signal processing according to the LMS algorithm. The adaptive filter 19a performs digital filter processing on the low frequency component xn of the audio signal using the coefficient determined by the LMS signal processing unit 19b and outputs a signal yn. As shown in FIG. 2, the adaptive filter 19a is configured by a FIR type digital filter, for example, delay elements DL, DL ... Which sequentially delay the input signal xn by one sampling time, and a coefficient w ₁ ( n), w ₂ (n), w ₃ (n) ・ ・ ・ w
It is realized by multiplication units ML, ML, ... For multiplying _N (n) and addition units AD, AD, ... For sequentially adding the outputs of the multiplication units.

The input signal at the current time n · Ts is xn,
The coefficient of each multiplier at₁(n), w ₂(n), w₃(n) ...
w_N(n) and the output is yn, the adaptive filter 19a
formula

[Equation 1] Then, the signal yn is output.

The LMS signal processing unit 19b receives the output signal en of the arithmetic unit 21 and the low frequency component xn of the audio signal as a reference signal, and includes these signals in the output signal en of the arithmetic unit 21. The LMS adaptive signal processing is performed so that the low frequency component of the audio signal to be reproduced becomes the minimum (= 0), and the coefficient of the adaptive filter 19a is determined. That is, the LMS adaptive signal processing unit 19b determines that the current time n · T
The coefficient of the adaptive filter 19a at s is w ₁ (n), w
₂ (n), w ₃ (n) ... w _N (n), the coefficients w ₁ (n + 1), w of the adaptive filter at time (n + 1) · Ts after one sampling time Ts ₂ (n + 1), w ₃ (n + 1) ... W _N (n + 1) are determined by the following equation (coefficient updating equation).

[0019]

[Equation 2]

The j-th filter coefficient updating formula is w _j (n + 1) = w _j (n) + μ × x (n-j + 1) × en (3). In the formula, (n) is the value at the current sampling time, (n + 1) is the value after one sampling time, (n-1) is the value before one sampling time, and (n-2) is the value before two sampling times. It means a value ... Further, μ is a constant (step size parameter) that determines the step of updating the coefficient of the adaptive filter. According to the adaptive signal processing, the coefficient of the adaptive filter 19a is determined so as to cancel the signal component having the correlation with the reference signal, and the signal yn is output from the adaptive filter.
Therefore, the signal yn becomes equal to the low frequency component of the audio signal included in the detection signal Sd at the observation point.

Audio signal Sa output from the entire operation audio source (not shown) is input to the equalizer 11. The equalizer 11 controls the gain of each band based on the frequency characteristic set by the equalizer characteristic setting unit (not shown), adds the frequency characteristic to the audio signal, and outputs the audio signal. The electronic volume 12 adjusts the audio signal level based on the volume setting value, and inputs the audio signal level to the speaker 14 a via the power amplifier 13. The speaker 14a emits an audio sound into the acoustic space based on the input audio signal, and the listener listens to music or the like. In parallel with the above, the signal xn in which the delay characteristic from the speaker 14a to the microphone 14c is added to the low frequency component of the audio signal Sa is input to the adaptive signal processing unit 19 as a reference signal. Also, microphone 1
Signal (detection signal) Sd at the observation point detected in 4c
Low-frequency component Sd 'and the output signal yn of the adaptive filter 19a.
And the difference (error signal) en is input to the adaptive signal processing unit 19.

The LMS signal processing section 19b performs the above-mentioned LMS adaptive signal processing to determine the coefficient of the adaptive filter 19a, and the adaptive filter 19a filters the reference signal xn based on the determined coefficient and outputs the signal yn. Is output. When such adaptive signal processing is repeated, the output signal yn
Ideally becomes equal to the low-frequency component of the audio signal included in the detection signal Sd ', and the output signal en of the calculation unit 21 does not include the low-frequency component of the audio signal and becomes only the noise signal. Further, the calculation unit 22 adds the output signal yn (low frequency component of the audio signal at the observation point) of the adaptive filter 19a and the high pass filter output (high frequency component of the audio signal at the observation point) to the audio signal Sa ₂ at the observation point. Is output.

As described above, the audio signal Sa ₂ at the observation point is input as the input 2 and the noise signal Sn at the observation point is input as the input 3 to the controller 23. Further, the audio signal Sa ₁ in which the delay characteristic from the speaker 14 a to the microphone 14 c is added to the audio signal Sa is input as the input 1 to the controller 23. The controller 23 uses inputs 1 to 3 to perform auto equalizing, noise masking, and automatic volume adjustment. Hereinafter, auto equalizing by the controller 23, masking of noise, and automatic volume adjustment (auto volume) will be described.

Auto-Equalizing FIG. 3 is a block diagram of the auto-equalizing controller in the controller 23. In auto-equalizing, the overall frequency characteristic including the acoustic space is controlled so as to be a desired characteristic. Hereinafter, the desired overall frequency characteristic will be described as a flat characteristic over the entire area.
Reference numeral 51 denotes a filter bank that separates / passes each frequency band component of the audio signal (input 1) Sa ₁ to which the delay characteristic of the acoustic space 14 is added, and is composed of a large number of band pass filters. Reference numerals 52a to 52n are block average calculation units for calculating and outputting averages of frequency band components within a predetermined time (called a block), 53 is an amplifier, 54 is an adder for adding block average values of each band component, 55a to 5
5n is a divider that divides each block average value by the total value of the block averages. The amplifier 53, the adder 54, and the dividers 55a to 55n form a normalization circuit whose total value is 1. The reason for normalization is that the level of each frequency band component of the audio signal Sa _{2 at} the observation point to be compared with the audio signal Sa ₁ is different. As will be described later, naturally, the frequency band components of the audio signal Sa _{2 at} the observation point are also normalized.

Reference numeral 61 is a filter bank for separating and passing each frequency band component of the audio signal (input 2) Sa _{2 at} the observation point, which is composed of a number of band pass filters. Reference numerals 62a to 62n are block average calculation units that calculate and output the average of each frequency band component within a predetermined time,
Reference numeral 63 is an amplifier, 64 is an adder that adds the block average values of the respective band components, and 65a to 65n are dividers, which divide each block average value by the total value of the block averages. The amplifier 63, the adder 64, and the dividers 65a to 65n form a normalization circuit whose total value is 1. Reference numerals 71a to 71n are calculation units that calculate the difference between each frequency band component (normalized) of the audio signal Sa ₁ output from the audio source and the audio signal Sa _{2 at} the observation point, and 73 is an equalizer during auto equalizing control. 2 is a frequency characteristic determination unit (gain determination unit) that determines the frequency characteristic (gain of each band).

The gain determining unit 75 determines the gain of each band so that the difference between the normalized value of each frequency band component of the audio signal Sa ₁ output from the audio source and the audio signal Sa _{2 at} the observation point becomes zero. Equalizer 1
1 is set to the gain variable amplifier 11b ₁ ～11Bn (see FIG. 1), the overall frequency characteristic is controlled to be flat. In addition, the equalizer 11 is used during the auto equalizing control.
The method of setting the gain is to determine the gain in the above control in real time, and only when the operation unit requests the auto equalizer, set the gain to the equalizer and fix it, during the auto equalizing control, in real time. A method of executing the above control to determine the gain and sequentially setting the gain in the equalizer, a method of determining the gain in the above control in real time during auto equalizing control, and a method of setting the latest gain in the equalizer between songs, etc. is there.

Noise Masking FIG. 4 is a block diagram of the noise masking control unit in the controller 23. Noise masking is control for correcting the frequency characteristic of the equalizer 11 based on the level of each frequency band component of noise. The audio sound is masked according to the noise level, and the listener cannot clearly hear the audio sound. Therefore, each frequency band component of noise is detected, and the frequency characteristic of the equalizer 11 is corrected based on the level of the component. In FIG. 4, 81 is a filter bank that separates / passes each frequency band component of the noise signal Sn (input 3), and is composed of a large number of band pass filters. Reference numerals 82a to 82n are block average calculation units that calculate and output the average of each frequency band component within a predetermined time, and 83 is a gain correction unit.

The gain correction unit 83 corrects the frequency characteristic (gain of each band) of the equalizer 11 based on the level of the noise Sn in each band. For example, if the noise level in a predetermined band is large is corrected as the equalizer gain of the band-increases, and sets the corrected gain to the gain variable amplifier 11b ₁ ~11bn. Specifically, a correspondence table between the normalized value of the noise component and the gain correction amount is stored, and the equalizer gain is corrected using the correspondence table. As a result, the audio sound is not masked by noise, and a clear audio sound can be heard. Incidentally, the second variable gain amplifier for respectively masking correction downstream of the variable gain amplifier 11b ₁ ~11bn (see FIG. 1) is provided, equalizer gain of band-when a predetermined band of the noise level is large in total manner The gain may be set in the second variable gain amplifier so as to increase the gain.

Auto Volume FIG. 5 is a block diagram of an auto volume control unit in the controller 23. The auto volume is a method of comparing the audio signal level and the noise level at the observation point and controlling the volume according to the ratio. In FIG. 5, 91 is a block averaging unit that calculates and outputs the average value of the audio signal Sa _{2 at} the observation point within a predetermined time, and 92 calculates the average value of the noise signal Sn at the observation point within the predetermined time. Output block average calculator, 9
3, 94 is an amplifier, 95 is a calculation unit for calculating the difference between the audio signal level and the noise signal level at the observation point,
Reference numeral 96 is a low-pass filter for adjusting the changing speed of the volume, and 96 is a volume determining section.

The volume determination unit 97 corrects the volume setting value V set by the volume based on the difference between the audio signal level and the noise signal level at the observation point and inputs it to the electronic volume 12 (see FIG. 1). That is, the volume determining unit 97 increases the volume when the noise signal level increases, so that the audio sound can be heard clearly. Specifically, the volume setting value V is adjusted according to the difference D between the audio signal level and the noise signal level, and V is input to the electronic volume 12 to control the volume. Although the present invention has been described above with reference to the embodiments, the present invention can be variously modified according to the gist of the present invention described in the claims, and the present invention does not exclude these.

[0031]

As described above, according to the present invention, auto equalizer control can be performed by determining the equalizer gain so as to obtain a desired total frequency characteristic without generating white noise. According to the present invention, the audio signal and the noise signal at the observation point are separated, and the gain of the equalizer is determined based on each band component of the audio signal at the observation point and the audio signal output from the audio source. Therefore, even when noise is generated, for example, even when running, or while listening to music, the equalizer gain is accurately determined so that the desired total frequency characteristic is obtained. Auto equalization can be performed.

Further, according to the present invention, the audio signal and the noise signal at the observation point are separated, the levels of the noise signal in a plurality of frequency bands are detected, and the frequency of the equalizer is increased so that the gain increases as the level increases. Since the characteristic is corrected, the correction for masking the noise can be performed according to the noise signal level, and a clear audio sound can be heard. Further, according to the present invention, the audio signal and the noise signal at the observation point are separated, and the volume is controlled based on the noise level. Therefore, even if the noise level increases, the volume is increased to listen to music. be able to.

[Brief description of drawings]

FIG. 1 is a block diagram of an audio device of the present invention.

FIG. 2 is a configuration diagram of an adaptive filter.

FIG. 3 is a configuration diagram of an auto equalizer control unit.

FIG. 4 is a configuration diagram of a masking correction control unit.

FIG. 5 is a configuration diagram of an automatic volume control unit.

FIG. 6 is a configuration diagram of a main part of a conventional audio device that realizes an auto equalizer function.

[Explanation of symbols]

 11-Equalizer 12-Electronic volume 14-Acoustic space 19-Adaptive signal processor 23-Controller

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H03H 21/00 8842-5J

Claims (3)

[Claims] 1. An equalizer for imparting a predetermined frequency characteristic to an audio signal output from an audio source,
In an audio device equipped with a speaker that receives an audio signal output from an equalizer and emits an audio sound into an acoustic space, a detection unit that detects sound at a predetermined observation point in the acoustic space, and a detection signal output from the detection unit A low-frequency component of the audio signal is input as a reference signal, and an adaptive signal processing unit that performs adaptive signal processing so as to cancel the low-frequency audio signal component included in the detection signal. An audio signal output unit for synthesizing a high frequency component of the audio signal included in the detection signal and a low frequency component of the audio signal at the observation point output from the adaptive signal processing unit to output an audio signal at the observation point; The audio signal output from the source and the audio signal at the observation point are divided into multiple frequency bands. And a frequency characteristic determination unit that determines the frequency characteristic of the equalizer so that the total frequency characteristic including the equalizer and the acoustic space becomes a predetermined frequency characteristic based on the level in each frequency band of both signals. Characteristic audio device. 2. An equalizer for imparting a predetermined frequency characteristic to an audio signal output from an audio source,
In an audio device equipped with a speaker that receives an audio signal output from an equalizer and emits an audio sound into an acoustic space, a detection unit that detects sound at a predetermined observation point in the acoustic space, and a detection signal output from the detection unit A low-frequency component of the audio signal is input as a reference signal, and an adaptive signal processing unit that performs adaptive signal processing so as to cancel the low-frequency audio signal component included in the detection signal. , A noise signal output unit that outputs a noise signal by subtracting the low-frequency component of the audio signal at the observation point output from the adaptive signal processing unit from the low-frequency component of the detection signal, and the noise signal levels in multiple frequency bands Frequency characteristic correction for detecting equalizer and correcting the frequency characteristic of the equalizer so that the gain increases as the level increases. An audio device having a section. 3. An equalizer for imparting a predetermined frequency characteristic to an audio signal output from an audio source,
A volume circuit that adjusts the level of the audio signal,
In an audio device equipped with a speaker that inputs a level-adjusted audio signal and emits an audio sound into an acoustic space, a detection unit that detects sound at a predetermined observation point in the acoustic space, and a detection signal that is output from the detection unit A low-frequency component is input, a low-frequency component of the audio signal is input as a reference signal, and an adaptive signal processing unit that performs adaptive signal processing so as to cancel the low-frequency audio signal component included in the detection signal, A noise signal output unit that outputs a noise signal by subtracting the low frequency component of the audio signal at the observation point output from the adaptive signal processing unit from the low frequency component of the detection signal, and volume control based on the level of the noise signal An audio device having a volume control section for controlling the volume.