JP2001025100A - Autographic equalizer and band level setting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To listen to music or the like in an optimal state by correcting change of frequency characteristics in a reproducing space by application to a multichannel audio system. SOLUTION: White noises are inputted to equalizers 12-14 on the side of a left channel, for example, a filter coefficient is changed step by step for each of divided bands of the respective equalizers 12-14, and a difference between a level for each frequency band outputted from a microphone 40 and the band level (target band level) set to a target band level setting part 32 is operated and stored in a memory 33 as an error. Afterwards, combination of the filter coefficients to minimize the error is extracted and the coefficients of the equalizers 12-14 are set. Next, concerning equalizer parts 15-17 on the side of the right channel, the coefficients are similarly set as well.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autographic equalizer for automatically adjusting a level (hereinafter, also referred to as "band level") for each frequency band of an audio signal, and in particular, to a speaker having four speakers around a listening point. The present invention relates to an autographic equalizer suitable for an audio system to be arranged.

[0002]

2. Description of the Related Art When music or the like is reproduced by an audio system, sound transmission characteristics are unique to the reproduction space due to reflection and absorption of sound in the reproduction space. The level at each frequency of the sound reaching the listener changes due to the transfer characteristics different for each reproduction space, which causes a feeling of strangeness. Therefore, it is preferable to correct the level of the audio signal for each frequency band according to the reproduction space.

Conventionally, there has been an autographic equalizer as a device for automatically adjusting the level of each frequency band. The auto graphic equalizer installs a microphone at the listening point, compares the signal supplied to the speaker with the signal output from the microphone,
This device automatically adjusts the band level of the signal supplied to the speaker.

In a general home audio system,
A so-called two-channel stereo system in which one speaker is arranged on each of the left and right sides in front of the listener is mainstream. A conventional autographic equalizer is intended for such a two-channel stereo system, and performs processing of individually adjusting the band level of the left and right audio signals.

[0005]

In a car audio system, there is a multi-channel stereo system in which speakers are arranged on the left and right sides of the front side and left and right sides of the rear side, and a speaker (woofer) dedicated to bass is arranged at the center of the rear side. Often adopted. Even in such an in-vehicle audio system, when adjusting the level for each frequency band using an autographic equalizer, a technique similar to that of home audio is conventionally used. That is, the left front and rear are single channels, and the right front and rear are single channels. For example, audio signals are simultaneously output from the left channel front and rear speakers and supplied to those speakers. After adjusting the band level, the sound is output simultaneously from the front and rear speakers of the right channel, and the band level of the audio signal supplied to those speakers is adjusted.

However, depending on the positions of the front and rear speakers, the sound waves from the front and rear speakers become out of phase at the position where the microphone is installed (hereinafter, referred to as a microphone point) due to the wave nature of the sound. They can cancel each other out. In this case, even if the gain of a predetermined band of the graphic equalizer for one channel is simply increased by the above-described method, there is a problem that the sound pressure does not increase at the microphone point and it is not possible to perform an appropriate correction.

[0007] To solve such a problem,
AC-3 of DVD (Digital Video Disk) playback device
(Multi-channel audio systems such as Dolby Laboratories) become increasingly important as they become mainstream. Accordingly, an object of the present invention is to provide an autographic equalizer that can be applied to a multi-channel audio system and that can correct changes in frequency characteristics due to a reproduction space and listen to music or the like in an optimal state.

[0008]

SUMMARY OF THE INVENTION The above-mentioned object is to provide a signal generator for generating a test signal, and a signal generator connected between the signal generator and a plurality of loudspeakers. A plurality of adjustable equalizer sections, a microphone installed at a listening point, a target band level setting section in which a target band level is set, and band level detection for detecting a band level of a signal output from the microphone Means, a band level comparing means for comparing a band level set in the target band level setting unit with a band level detected by the band level detecting means to detect an error for each frequency band, and the band level comparing means Storage means for storing the error detected in the above, according to the error for each frequency band stored in the storage means And control means for adjusting the band level of the serial equalizer, solved by the automatic graphic equalizer, characterized in that it comprises a.

The above-mentioned problem is solved by setting a target band level in target band level setting means, arranging a microphone at a listening point, supplying a test signal to a speaker via an equalizer section, While changing the coefficient, the error of the band level output from the microphone with respect to the band level set in the target band level setting means is stored in the storage means, and the coefficient of the equalizer unit is minimized so that the error is minimized. The problem is solved by a band level setting method characterized by setting.

The operation of the present invention will be described below. In the present invention, a target band level is set in the target band level setting means. Then, an error between the band level of the signal output from the microphone and the target band level is detected while changing the coefficient of the equalizer section, and stored in the storage means. Thereafter, a combination of coefficients that minimizes an error is extracted, and coefficients of each equalizer section are set according to the extracted combination of coefficients.

As described above, in the present invention, the band level at the listening point is measured by variously changing the coefficient of the equalizer section, and based on the measurement result, the frequency characteristic of the equalizer section is optimized so that the frequency characteristic at the listening point becomes the best. Set the coefficient. Thus, different transfer characteristics can be corrected for each reproduction space, and audio can be enjoyed in the best condition.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an overall configuration of an autographic equalizer according to an embodiment of the present invention. This embodiment shows an example in which the present invention is applied to an autographic equalizer that adjusts the frequency characteristics of an in-vehicle audio system.

The autographic equalizer according to the present embodiment includes a sound source 10, a changeover switch 11, graphic equalizer units 12 to 17, a mixer 18, signal delay units 19 to 23, amplifiers 24 to 28, a filter Bank unit 29, band level calculation unit 30, band level comparison unit 31, target band level setting unit 32, memory 33, filter coefficient selection / setting unit 34, control unit 35
It is composed of A left front speaker 41, a left rear speaker 42, a right front speaker 43, a right rear speaker 44, and a bass woofer 45 are attached to the vehicle. Further, a microphone 40 is provided at the listening point (driver's seat).

The sound source 10 can generate white noise (or pink noise) and can generate a time stretched pulse (TSP). The changeover switch 11 converts the signal output from the sound source 10 into a graphic equalizer unit 12 for the left channel,
13, 14 or one of the right channel graphic equalizer units 15, 16, 17 selectively. When actually listening to music or the like, an audio signal output from a music source such as a CD player or an FM tuner is input to each of the graphic equalizer units 12 to 17 via the changeover switch 11.

The graphic equalizer units 12 to 17
In each case, the filter coefficient is set by the filter coefficient selection / setting unit 34, and the level of each audio signal in the frequency band is adjusted according to the filter coefficient. The signal output from the graphic equalizer unit 12 is output to the signal delay unit 1.
9, is input to the amplifier 24, is amplified by the amplifier 24, and is supplied to the left front speaker 41. The signal output from the graphic equalizer 13 is input to the amplifier 25 via the signal delay unit 20, amplified by the amplifier 25, and supplied to the left rear speaker 42. Further, the signal output from the graphic equalizer unit 15 is input to the amplifier 26 via the signal delay unit 21, amplified by the amplifier 26, and supplied to the right front speaker 43. Furthermore, the signal output from the graphic equalizer unit 16 is input to the amplifier 27 via the signal delay unit 22, and is amplified by the amplifier 27.
It is supplied to the right rear speaker 44. Furthermore, the signals output from the graphic equalizer unit 14 and the graphic equalizer unit 17 are mixed by the mixer 18 and
After being input to the amplifier 28 through the signal delay unit 23 and amplified by the amplifier 28, the woofer 4 arranged at the rear center is
5 is supplied. The delay times in the signal delay units 19 to 23 and the amplification factors in the amplifiers 24 to 28 are all controlled by the control unit 30.

The microphone 40 arranged in the driver's seat is
The sound waves emitted from the speakers 41 to 45 are input, converted into electric signals, and output. The filter bank unit 29
The signal output from the microphone 40 is input and divided into frequency bands corresponding to the divided bands of the graphic equalizer units 12 to 17. The band level calculation unit 30 calculates a level (band level) for each frequency band output from the filter bank unit 29. In the target band level setting unit 32, a target band level (for example, a band level according to a user's favorite frequency characteristic such as flat or high rise) is set in advance. The band level comparison unit 31 compares the band level (target band level) set in the target band level setting unit 32 with the band level (detection band level) output from the band level calculation unit 30, and determines each frequency band. The level difference between the two is calculated every time. The calculation result of the level difference is used as an error in
To memorize.

The control unit 35 controls the filter coefficient selection / setting unit 34 according to the error stored in the memory 33, and sets the filter coefficients of the graphic equalizer units 12 to 17. Further, as described above, the control unit 35
The signal delay time in the signal delay units 19 to 23 and the amplification factor in the amplifiers 24 to 28 are set. FIG. 2 is a block diagram showing a configuration of the graphic equalizer units 12 to 17. Each of the graphic equalizer units 12 to 17 is configured by serially connecting a plurality (n) of band filters BAND1 to BANDn. Each band filter BAND
1 to BANDn are all four delay elements (Z ^-1 ) 51
, Five filter coefficient units 52, and one mixer 53, and the level of each frequency band can be changed by adjusting the gain of each filter coefficient unit 52. . That is, the graphic equalizer units 12 to 17 change the level of each frequency band (band) from -12 dB to +1 as shown in FIG.
It can be changed in units of 1 dB up to 2 dB.

FIGS. 4 and 5 are flowcharts showing the operation of the automatic graphic equalizer configured as described above. FIG. 4 shows the signal delay units 19 to 2 so that the distance from each speaker to the listening point is equal in audibility.
3 shows a process for adjusting the delay time, and FIG. 5 shows a process for adjusting the level for each frequency band of the right channel and the left channel.

First, in step S11, the sound source 10
Output white noise (or pink noise). Then, in step S12, each speaker 4
The gains of the amplifiers 24 to 28 are adjusted so that the volume of white noise (or pink noise) output from 1 to 45 becomes constant. Specifically, one speaker (4
Only the white noise (or pink noise) is supplied to any one of the amplifiers (1 to 45), and the gain of the corresponding amplifier (any one of 24 to 28) is gradually increased from the minimum value. When the signal output from the microphone 40 reaches a certain level, the gain of the amplifier that supplies the signal to the speaker is fixed. This is sequentially performed on all the speakers 41 to 44 to adjust the volume of white noise (or pink noise) output from each of the speakers 41 to 45.

Next, the process proceeds to step S13, where the impulse response is measured for each of the speakers 41 to 45, and the delay time of the signal delay units 19 to 23 is set according to the measurement result. That is, the time extension pulse (TSP) generated by the sound source 10 is sequentially supplied to the speakers 41 to 45. Then, the output of the microphone 40 is analyzed, and the propagation time from the generation of the time extension pulse to the arrival at the microphone 40 is measured for each speaker. afterwards,
The maximum time among these propagation times is defined as T M, and the delay time of the signal delay units 19 to 23 is set according to the difference (T M -T m) from the propagation time t M of the other speakers. The output signal has a uniform propagation time.

Thereafter, the processing shown in FIG. 5 is started. That is, first, in step S21, the sound source 10 outputs white noise (or pink noise). Then, the process proceeds to step S22, and the switch 11 supplies white noise (or pink noise) to only one of the left channel and the right channel. Here, it is assumed that white noise (or pink noise) is initially supplied to the left channel side.

Thereafter, the flow shifts to step S23, where the graphic equalizer sections 12, 13, 14 for the left channel are set.
-12d for each band filter BAND1 to BANDn
One level from B to +12 dB is selected and a coefficient is set. For example, first, each band filter BAND
The coefficients of the band filters BAND1 to BANDn are set so that the levels of 1 to BANDn are all -12 dB.
Thereafter, in step S24, the level (detection band level) for each frequency of the signal output from the microphone 40 is calculated by the band level calculation unit 30 and compared with the target band level set in the target band level setting unit 32. I do. Then, an error between the target band level and the detected band level is stored in the memory 33.

Next, in step S25, it is determined whether or not the detection level and the target band level have been compared for all combinations of coefficients. If not, the process returns to step S23, where the graphic equalizer units 12, 13,
14 is selected, and the level of each frequency of the band filters BAND1 to BANDn of the graphic equalizer is set to 1
The difference between the detected band level and the target band level is stored in the memory 33 while being changed step by step. In this way, for each of the graphic equalizer units 12, 13, and 14, the detected band level and the target band level are compared for all combinations of coefficients.

In step S25, it is determined whether or not the comparison between the detected band level and the target band level has been completed for all combinations of coefficients. If it is determined that the comparison has been completed, the process proceeds to step S26. In step S26, the coefficient closest to the target band level is selected for each of the band filters BAND1 to BANDn of each of the graphic equalizer units 12 to 17 with reference to the error data stored in the memory 33. The selected coefficients are given to a filter coefficient selection setting unit 34, and the graphic equalizer units 12, 1
Coefficients for each band of 3 and 14 are set.

Thereafter, the flow shifts to step S27, where it is determined whether or not the setting of the coefficients of the left channel and the right channel has been completed. Here, since the right channel has not yet been reached, the process proceeds to step S22, and the changeover switch 11 is switched to the right channel side. And, as above,
Graphic equalizer section 15, 1 for right channel
Coefficients 6 and 17 are set for each band.

In this embodiment, as described above, the coefficient of the equalizer section of each channel is variously changed and compared with the target band level, and the band level (detection band level) at the listening point is most likely to be the target band level. The coefficients of the equalizer units 12 to 17 are set so as to be close to each other. As a result, the effect of interference between sound waves output from the front speakers and sound waves output from the rear speakers is reduced, and even in a multi-channel stereo system in which four or more speakers are arranged around a listening point, frequency characteristics can be improved. It can be corrected to an optimal state.

In this embodiment, the case where the left and right front, the left and right rear, and the woofer each have one speaker has been described. However, the present invention is also applied to an audio system having two front speakers, two right and left. Can also. In the present invention, the processing shown in FIG. 4 is not essential. For example, when there is almost no difference in propagation time from each speaker to the microphone, there is no inconvenience even if it is omitted.

Further, in the above embodiment, an example has been described in which the present invention is applied to a car audio system, but the present invention can also be applied to a home audio system.

[0029]

As described above, according to the present invention,
Measures the band level at the listening point by changing the coefficient of the equalizer section in various ways, compares it with the target band level, and sets the coefficient of the equalizer section according to the result, so it can support multi-channel audio systems Thus, different transfer characteristics can be corrected for each reproduction space, and the audio can be enjoyed in the best condition.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an autographic equalizer according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a graphic equalizer unit.

FIG. 3 is a schematic diagram illustrating a change in level of each frequency band of a graphic equalizer unit.

FIG. 4 is a flowchart (part 1) illustrating an operation of the autographic equalizer according to the embodiment;

FIG. 5 is a flowchart (part 2) illustrating an operation of the autographic equalizer according to the embodiment;

[Explanation of symbols]

 Reference Signs List 10 sound source, 11 changeover switch, 12-17 graphic equalizer section, 18 mixer, 19-23 signal delay section, 24-28 amplifier, 29 filter bank section, 30 band level calculation section, 31 band level comparison section, 32 target band Level setting section, 33 memories, 34 filter coefficient selection / setting section, 40 microphones, 41 to 44 speakers, 45 woofer, 51 delay element, 52 filter coefficient section.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G10K 15/00 L

Claims (3)

[Claims] A signal generation unit for generating a test signal; a plurality of equalizer units connected between the signal generation unit and a plurality of speakers, each of which can adjust a band level of a signal supplied to each speaker; A microphone installed at a listening point, a target band level setting unit in which a target band level is set, a band level detection unit that detects a band level of a signal output from the microphone, and the target band level setting unit Band level comparing means for detecting an error for each frequency band by comparing the band level set in the band level with the band level detected by the band level detecting means; and storing means for storing the error detected by the band level comparing means. And the band level of the equalizer section according to the error for each frequency band stored in the storage means. Auto graphic equalizer, characterized in that it comprises a control means for adjusting the Le, the. 2. The autographic equalizer according to claim 1, further comprising delay means for delaying signals supplied to the plurality of speakers by a predetermined time. 3. A target band level is set in target band level setting means, a microphone is arranged at a listening point, a test signal is supplied to a speaker via an equalizer, and a coefficient of the equalizer is changed. And storing an error of a band level output from the microphone with respect to a band level set in the target band level setting means in a storage means, and setting a coefficient of the equalizer section so that the error is minimized. A band level setting method characterized by the following.