JPH0774565A - System for automatically correcting frequency characteristic in automobile compartment - Google Patents

Abstract

PURPOSE:To automatically and optimally set parameters by setting the parameters of an equalizer including at least a center frequency, an acute angle and gain and correcting the peculiar peak and dip of frequency characteristics. CONSTITUTION:M group signals are reproduced by a speaker and the response is acquired by a binaural microphone present at a listening position. In this case, the response is acquired by a right ear microphone 81 at the time of reproducing a right side speaker 71 or 73 and by a left ear microphone 82 at the time of reproducing a left side speaker 72 or 74. Then, the response of the M-sequence obtained by utilizing the fast M-sequence transformation is converted to an impulse reponse. Then, fast Fourier transformation is performed to the impulse response, the frequency characteristics are calculated and the peculiar peak and dip in the frequency characteristics are corrected. At the time, the center frequency fc, the acute angle Q and the gain G are set for the number of the bands of the equalizer as the parameters of the equalizer. Then, the parameters for correcting the frequency characteristics in an automobile compartment can be automatically and optimally set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle interior frequency characteristic automatic correction system for automatically setting parameters of an equalizer for correcting frequency characteristics inside a vehicle compartment.

[0002]

2. Description of the Related Art Generally, frequency characteristics in a vehicle compartment show a complicated characteristic with a unique peak or dip for each vehicle. Therefore, in a commercially available car audio system, an equalizer (equal) for correcting such frequency characteristics is used.
izer) is often provided.

[0003]

The correction by the equalizer is left to the user, but it is almost difficult to make the optimum correction by the sense of hearing.

In view of such circumstances, an object of the present invention is to provide a vehicle interior frequency characteristic automatic correction system that optimally and automatically sets a parameter of an equalizer for correcting the frequency characteristic inside the vehicle compartment.

[0005]

SUMMARY OF THE INVENTION The present invention uses an M-sequence (maximum period sequence) signal that is effective for measurement with a high SN ratio (signal to noise ratio) compared to other measurement signals. The above object is achieved by, for example, executing the processing for obtaining the optimum curve of the equalizer from the frequency characteristic by using a digital signal processor (DSP).

That is, the vehicle interior frequency characteristic automatic correction system according to the present invention is a system for automatically setting the parameters of an equalizer for correcting the frequency characteristic in the vehicle interior, which reproduces an M-sequence signal by a speaker, M-sequence response acquisition means for acquiring an M-sequence response, which is a response of the M-sequence signal, with a microphone placed at a listening position in the vehicle compartment, and impulse response conversion for converting the M-sequence response into an impulse response by high-speed M-sequence conversion Means, frequency characteristic calculation means for performing a fast Fourier transform on the impulse response to calculate frequency characteristics, and at least a center frequency, a sharpness and a gain for correcting characteristic peaks and dips of the frequency characteristics. And equalizer parameter setting means for setting equalizer parameters including.

[0007]

In the vehicle interior frequency characteristic automatic correction system configured as described above, the M-sequence signal is reproduced from the speaker, and its response is obtained by the microphone placed at the listening position in the vehicle interior. The M-sequence response is a high-speed M
It is converted into an impulse response by series conversion. And
A fast Fourier transform is performed on the impulse response, and the frequency characteristic is calculated. Then, the equalizer parameters including at least the center frequency, the sharpness and the gain for correcting the characteristic peak and dip of the frequency characteristic are set.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram showing a hardware configuration of a vehicle interior frequency characteristic automatic correction system according to an embodiment of the present invention. In FIG. 1, reference numeral 10 is a microcomputer, reference numeral 20 is a digital signal processor (DSP), reference numeral 30 is a digital / analog (DA) converter, reference numeral 40 is an analog / digital (AD) converter, reference numeral 50 and 60 is an amplifier, reference numeral 71
Is a front right speaker, reference numeral 72 is a front left speaker, reference numeral 73 is a rear right speaker, reference numeral 74 is a rear left speaker, reference numeral 81 is a right ear microphone, reference numeral 82 is a left ear microphone, and reference numeral 90 is a sound field. The microphones 81 and 82
Are placed in the listening position.

Next, the signal processing procedure executed by the microcomputer 10 and the DSP 20 in the configuration of FIG. 1 will be described with reference to the flowchart of FIG. First, the M-sequence signal is reproduced from one of the speakers, and its response is acquired by the binaural microphone at the listening position (step 10).
2). However, when the right speaker, that is, the speaker 71 or 73 is reproduced, the right ear microphone 81 acquires the response, and when the left speaker, that is, the speaker 72 or 74 is reproduced, the left ear microphone 82 acquires the response.

Next, the obtained M-sequence response is converted into an impulse response by utilizing the fast M-sequence conversion (step 104). Since the high speed M-sequence conversion is well known, its description is omitted here. Next, a fast Fourier transform (FFT) is performed on the impulse response to calculate the frequency characteristic (step 106). Finally, equalizer parameters (center frequency f _C , sharpness Q, gain G) for correcting characteristic peaks and dips in the frequency characteristic are set for the number of equalizer bands (step 108). However, the right channel equalizer is used for the right ear, and the left channel equalizer is used for the left ear. With the above processing, the parameters of the equalizer for correcting the frequency characteristic in the vehicle interior are optimally and automatically set.

Further, in the present embodiment, when equalizers are provided for the front and the rear respectively, first, the M-sequence signal is reproduced from the front speaker and the parameters of the front equalizer are set. Next, the M-series signal is reproduced from the rear speaker and the parameters of the rear equalizer are set. In this way, the front and rear equalizers are set independently.

Further, in the present embodiment, the frequency characteristic obtained as a result of FFT is divided into 1/3 octave bands, and the spectrum of each band is calculated. And this one
Set the equalizer parameters based on the / 3 octave frequency characteristics. As a result, it becomes possible to make a correction closer to the sense of hearing.

Further, when the 1/3 octave frequency is calculated, the center frequency of the 1/3 octave band is swept at arbitrary intervals to obtain a finer 1/3 octave band.
Calculate octave frequency characteristics. Then, the equalizer parameters are set based on this characteristic. As a result, the equalizer parameters (f _C , Q, G) can be set more precisely.

Further, in setting the equalizer parameters, first, the equalizer parameters for one band of one channel are set for one characteristic peak or dip of the frequency characteristic, and then the equalizer parameters are set through the equalizer. The frequency characteristic is measured, and the equalizer parameters for one band of the other channel are set.
By thus setting the equalizer parameters alternately for each band, it is possible to improve the correction accuracy.

Although one embodiment of the present invention has been described above, of course, the present invention is not limited to this, and it is easy for those skilled in the art to devise various embodiments. For example, in this embodiment, the system is realized by a digital signal processor (DSP) and a microcomputer, but it may be realized by only the microcomputer.

[0017]

As described above, the correction of the frequency characteristic according to the present invention has the following advantages as effects. (1) By using the M-sequence signal, it is possible to measure the frequency characteristic with high accuracy, and therefore the parameter of the equalizer that corrects the frequency characteristic also has high accuracy. (2) Moreover, the user can easily set such precise equalizer parameters.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing a hardware configuration of a vehicle interior frequency characteristic automatic correction system according to an embodiment of the present invention.

FIG. 2 is a schematic flowchart showing a signal processing procedure in the vehicle interior frequency characteristic automatic correction system according to the embodiment of the present invention.

[Explanation of symbols]

 10 ... Microcomputer 20 ... Digital signal processor 30 ... Digital / analog converter 40 ... Analog / digital converter 50 ... Amplifier 60 ... Amplifier 71 ... Front right speaker 72 ... Front left speaker 73 ... Rear right speaker 74 ... Rear left speaker 81 … Right ear microphone 82… Left ear microphone 90… Sound field

Claims (5)

[Claims] 1. A system for automatically setting a parameter of an equalizer for correcting a frequency characteristic in a vehicle interior, wherein an M sequence signal is reproduced by a speaker, and an M sequence response which is a response of the M sequence signal is produced in the vehicle interior. M sequence response acquisition means for obtaining with a microphone placed at a listening position, impulse response conversion means for converting the M sequence response into an impulse response by high speed M sequence conversion, and fast Fourier transform for the impulse response. Done,
Frequency characteristic calculation means for calculating frequency characteristics, for correcting characteristic peaks and dips of the frequency characteristics, at least center frequency, equalizer parameters including sharpness and gain, equalizer parameter setting means, A vehicle interior frequency characteristic automatic correction system comprising. 2. The M-sequence response acquisition means, the impulse response conversion means, the frequency characteristic calculation means, and the equalizer parameter setting means, when there are equalizers for the front and the rear, respectively, first, a speaker from the front is used. It is configured to set the parameters of the front equalizer by reproduction, and then set the parameters of the rear equalizer by reproduction from the rear speaker,
The vehicle interior frequency characteristic automatic correction system according to claim 1. 3. The equalizer parameter setting means,
The frequency characteristic calculated by the frequency characteristic calculating means is divided into 1/3 octave bands to calculate the spectrum of each band, and the equalizer parameters are set based on the 1/3 octave frequency characteristics. The automatic frequency characteristic correction system for the vehicle interior. 4. The vehicle interior frequency characteristic automatic correction system according to claim 3, wherein the calculation of the 1/3 octave frequency characteristic is performed by sweeping the center frequency of the 1/3 octave band at an arbitrary interval. 5. The setting of the equalizer parameters includes:
The parameter of the equalizer for one band of one channel and the parameter of the equalizer for one band of the other channel are set alternately.
The vehicle interior frequency characteristic automatic correction system according to claim 1.