JPH0965483A - In-cabin frequency characteristic automatic correction system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an in-cabin frequency characteristic automatic correction system in which a frequency characteristic balance natural in auditory feeling is obtained by applying various conversion to signals obtained from a microphone so as to calculate phase difference characteristics of left and right ears and correcting the characteristics based on frequencies band where the left and right ears are not opposite in phase to each other. SOLUTION: Microphones 41, 42 receive sounds from speakers 31-34 and their signals are fed to an A/D converter 23 and a frequency characteristic arithmetic section 13. The arithmetic section 13 converts the signal into an impulse response. High speed Fourier transform is applied to the impulse response and frequency characteristics for left and right ears are calculated and a phase characteristic and a phase difference characteristic are calculated from them. A inverted band where the phases are opposite is searched from the phase difference characteristic. In this band, a boost correction to increase the gain of an equalizer section 12 for in-cabin characteristic correction is not conducted. A frequency for a correction point is decided for the band where phases are not opposite and a parameter of the correction equalizer section 12 is set based on the frequency and the frequency characteristic is automatically corrected.

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, and more particularly to a vehicle interior frequency characteristic automatic correction system for automatically setting the parameters of an equalizer for correcting the frequency characteristic inside the vehicle interior. Regarding

[0002]

2. Description of the Related Art In a conventional vehicle interior frequency characteristic automatic correction system, an M-sequence signal is reproduced by a speaker, and the reproduced signal is for left and right ears arranged at a listening position in the vehicle interior. Of each microphone, and after converting the signal (M sequence response signal) acquired by each microphone into an impulse response,
Fast impulse Fourier transform (FFT) is applied to the impulse response to calculate frequency characteristics, and the equalizer parameters (center frequency,
The sharpness and gain etc.) were set to correct the frequency characteristics in the passenger compartment.

[0003]

However, the above-described conventional vehicle interior frequency characteristic automatic correction system has the following problems. Due to the fact that the speakers are laid out asymmetrically in the passenger compartment, and there is sound reflection from nearby glass windows, etc., the frequency characteristics inside the passenger compartment have a dip in the middle range (200 Hz to 2 kHz). In many cases, the phase in the left ear and the phase in the right ear are opposite at the dip point. Even if the left and right ears are out of phase with each other, boosting the dip point with the equalizer (increasing the gain) causes the listener in the vehicle compartment to feel uncomfortable.

The present invention has been made in view of the above problems, and boosting correction is not performed for a frequency band in which the phase at the listening position of the right ear is opposite to the phase at the listening position of the left ear. It is an object of the present invention to provide an automatic vehicle interior frequency characteristic correction system capable of ensuring a natural frequency characteristic balance in terms of hearing.

[0005]

In order to achieve the above object, an automatic vehicle frequency characteristic correction system according to the present invention reproduces an M-sequence signal by a speaker and reproduces it by the speaker. The obtained signal is acquired as an M-sequence response signal by a microphone arranged in the vehicle compartment, the M-sequence response signal is converted into an impulse response, and then the impulse response is subjected to a fast Fourier transform (FFT) to obtain a frequency characteristic. In the vehicle interior frequency characteristic automatic correction system for automatically determining the frequency characteristic in the vehicle interior by setting the parameters of the equalizer based on the peak and the dip that characterize the frequency characteristic, the impulse response is high-speed. Phase characteristic calculating means for calculating the phase characteristic at each listening position of the left ear and the right ear based on the frequency characteristic obtained by applying the Fourier transform, and the phase characteristic Phase difference calculation means for calculating the phase difference between the left and right ears based on the phase characteristics calculated by the output means, and the listening position of the left ear and the right ear based on the phase difference calculated by the phase difference calculation means Search the band where the phase at the listening position is out of phase, set the equalizer parameters based on the frequency characteristics other than the band where the phase is out of phase, and change the vehicle interior frequency characteristics. It is characterized by comprising a frequency characteristic correcting means for correcting.

In the above-mentioned vehicle interior frequency characteristic automatic correction system, the frequency characteristic correction means causes the frequency other than the band in which the phase at the listening position of the left ear is opposite to the phase at the listening position of the right ear. The equalizer parameters are set based on the characteristics. Accordingly, even if the dip point on the frequency characteristic is the opposite phase of the dip point, the gain of the equalizer is not increased and the boost is not corrected. Therefore, when the above-mentioned vehicle interior frequency characteristic automatic correction system is used, unnatural hearing correction is eliminated, so that the listener in the vehicle interior will not feel uncomfortable, and a audible natural frequency characteristic balance will be realized. be able to.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram showing the configuration of a vehicle interior frequency characteristic automatic correction system according to an embodiment. Left and right front speakers 31, 3 in the passenger compartment
2, left and right rear speaker 33, 34 and speaker 31-
Left and right microphones 41 and 42 are arranged corresponding to the positions of both ears of the human body in order to capture the sound from the microphone 34. 1
Is a digital signal processor (hereinafter referred to as DSP) that processes signals, and DSP 1 is an M-series signal generator 11 that generates an M-series signal, and a vehicle interior characteristic correction that corrects a spatial frequency characteristic in the vehicle interior The equalizer unit 12, the frequency characteristic calculation unit 13 for calculating the frequency characteristic from the response of the measurement signals of the microphones 41, 42 in the vehicle compartment, and the control unit 14 for controlling them are included. 21
Is a D / A converter for converting the digital signal processed by the vehicle interior characteristic correction equalizer unit 12 into an analog signal, 22 is an amplifier for amplifying the audio signal converted by the D / A converter 21, and the output side is the vehicle interior Of the speakers 31 to 34. 23 is a DSP for outputting signals from the microphones 41 and 42
1 is an A / D converter for converting into a digital signal in order to perform digital signal processing.

FIG. 2 is a flow chart showing the operation of the DSP 1, and FIGS. 3 (a) to 3 (c) are waveform charts schematically showing the frequency characteristics of signals in each processing.
(D) is a waveform diagram showing an example of a phase difference characteristic between the left and right ears. Hereinafter, the vehicle interior frequency characteristic automatic correction method according to the embodiment of the present invention will be described with reference to FIGS. 2 and 3.

Step 1: The control section 14 instructs the M-series signal generation section 11 to generate an M-series signal and transmit it to the vehicle interior characteristic correction equalizer section 12. The M-sequence signal is sent to the speakers 31 to 34 in the vehicle compartment via the D / A converter 21 and the amplifier 22 to be converted into sound and reproduced. On the other hand, the microphones 41 and 42 arranged at the listening position in the vehicle compartment receive the voices from the speakers 31 to 34, and this signal is converted into a digital signal by the A / D converter 23 and is then sent to the frequency characteristic calculation unit 13. Sent.

Step 2: In the frequency characteristic calculation unit 13, the M-sequence response signals heard by the microphones 41 and 42 are subjected to high-speed M-sequence conversion and converted into impulse responses (see FIG. 3A). Step 3: Fast impulse Fourier transform (F
FT) is performed, and the frequency characteristics (see FIG. 3B) and the phase characteristics of the left and right ears received by the microphones 41 and 42 are calculated.

Step 4: The binaural average frequency characteristic is calculated. That is, the average value of the frequency characteristics of the left and right ears is obtained. A 1/3 octave band power spectrum is created based on the binaural average frequency characteristic (FIG. 3).
(C)). Step 5: Search for peak P and dip D based on the 1/3 octave band spectrum (Fig. 3 (c)).
reference).

Step 6 to Step 7: Next Step 6
At, in the frequency band in which the phase difference between the two ears is calculated from the phase characteristics obtained in step 3 (see FIG. 3D), the phase in the left ear and the phase in the right ear are opposite phases, Mainly the mid-range (200 Hz to 2 KHz) is searched (step 7).

Step 8: From the search result in Step 5 and the search result in Step 7, the frequency to be the correction point is determined. In this case, as the correction point, a frequency whose phase is not opposite is selected. Therefore, when the band of the dip P searched in step 5 has the opposite phase, the frequency characteristic is not corrected even if it is a dip. Step 9: The parameters to be corrected in the vehicle interior characteristic correction equalizer unit 12 are set based on the frequency determined in Step 8.

As described above, in the vehicle interior frequency characteristic automatic correction system according to the embodiment of the present invention,
Even if the dip P is due to frequency characteristics, dip P
If the phases of the left and right ears in are opposite,
Boost is not corrected. Therefore, it is possible to make a natural hearing correction.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the operation of the DSP.

3A to 3C are waveform charts schematically showing frequency characteristics of signals in each processing, and FIG. 3D is a waveform chart showing an example of phase difference characteristics between the left and right ears. is there.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DSP 11 M sequence signal generation unit 12 Equalizer unit for vehicle interior characteristic correction 13 Frequency characteristic calculation unit 14 Control unit 31, 32, 33, 34 Speaker 41, 42 Microphone

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H04S 7/00 G10K 15/00 M

Claims (1)

[Claims] 1. A M-sequence signal is reproduced by a speaker, and a signal reproduced by the speaker is acquired as an M-sequence response signal by a microphone arranged at a listening position in a vehicle compartment. Is converted into an impulse response, the impulse response is subjected to fast Fourier transform (FFT) to obtain the frequency characteristic, and the equalizer parameters are set based on the peak and the dip characterizing the frequency characteristic. In the vehicle interior frequency characteristic automatic correction system that automatically corrects the frequency characteristic in the vehicle interior, at each listening position of the left ear and the right ear based on the frequency characteristic obtained by performing the high-speed Fourier transform on the impulse response. Phase characteristic calculating means for calculating the phase characteristic; phase difference calculating means for calculating the phase difference between the left and right ears based on the phase characteristic calculated by the phase characteristic calculating means; A band in which the phases at the listening position of the left ear and the listening position of the right ear are opposite phases based on the phase difference calculated by the phase difference calculating means is searched, and the band in which the phases are opposite phases. A vehicle interior frequency characteristic automatic correction system comprising: a frequency characteristic correction means for setting an equalizer parameter based on frequency characteristics other than the above and correcting the vehicle interior frequency characteristic.