JPH04170300A - Sound image locarization controller - Google Patents

Abstract

PURPOSE:To enable sound to reach a listener from left and right speakers at the same time by delaying left and right signals from a sound source depending on a difference of a maximum time maximizing a correlation between an output and the left and right signals from a sound source. CONSTITUTION:A signal B of microphones 10L,10R and an output signal A of a delay circuit 7 are given to a high pass filter 12, the signals are converted into digital signals by A/D converter sections 24L,24R, and they are inputted to correlation calculation sections 26L,26R. The calculation sections 26L,26R obtain correlation of the signal B with respect to the signal A with left and right channels. Maximum value detection sections 27L,27R obtain a time maximizing the mean value of the correlation, and a right time difference calculation section 28 obtains a time difference. A microcomputer 11 uses a delay control signal so as to control the delay time of the delay circuit 7 in response to the code of the result of calculation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sound image localization control device in a vehicle-mounted sound reproduction system or the like.

[Summary of the Invention] The present invention provides a sound reproduction system that includes a delay unit that delays left and right signals emitted from a sound source and a speaker that reproduces the delayed left and right signals. Microphones are placed on the left and right sides of the vicinity, and the first and second cross-correlation functions are calculated based on the delayed left and right signals and the signals from the left and right microphones, and these cross-correlation functions are By finding the maximum time for each, then calculating the difference between these maximum times and controlling the delay time of the delay section, the sound reaches the listener from the left and right speakers at the same time. Become.

[Prior Art] Fig. 2 shows an example of speaker arrangement positions and listening positions in an automobile equipped with an in-vehicle sound reproduction system.Door speakers 1 and 2 are installed on the front left and right doors of the automobile, respectively. , and rear speakers 3 and 4 are placed on the left and right sides of the rear side of the vehicle, respectively.

[Problems to be Solved by the Invention] Generally, the arrangement of speakers inside a car is asymmetrical when viewed from the listener 5.

Speaker 1 located at an asymmetrical position (distance)
The sounds reproduced from ~4 reach the listener with a time difference. If there is a difference in arrival time, the sound image will be localized toward the sound source that arrives first due to the Haas effect.

Therefore, there is a method of using a delay concave path to delay the signal that arrives first, so that the left and right channel signals arrive at the same time. However, with this method alone, if the position of the seat or the backrest is moved and the position of the head (ears) changes, the arrival time from the left and right speakers will change and the localization will shift.

[Means for Solving the Problems] In order to achieve the second object, the present invention includes a delay unit that delays the left and right signals output from the acoustic source by delay times corresponding to delay control signals, respectively. , left and right speakers installed on the left and right sides respectively and reproducing left and right signals delayed by a delay section, left and right microphones placed on the left and right sides near the listener, respectively, a calculation unit that calculates each cross-correlation function based on the left and right signals and signals from the left and right microphones; a maximum value detection unit that calculates the maximum value time at which each cross-correlation function reaches its maximum; The device includes a calculation unit that calculates a difference between values and times, and a control unit that outputs a delay control signal based on this time difference.

[Operation] In the present invention, microphones are provided on the left and right sides near the listener, and the cross-correlation functions between these outputs and the left and right signals from the sound source are calculated, and each of these cross-correlation functions is maximized. Since the maximum value time is determined and the left and right signals from the sound source are delayed using the difference between them, it is possible to ensure that the sound reaches the listener from the left and right speakers at the same time.

[Example code] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of the sound image localization control device according to the present invention, in which 6 is a playback device such as a CD player, 7 is a delay circuit, 8 is a switch circuit, 9L and 9R are amplifiers, and I
OL and IOR are microphones installed near the listener, for example, on the left and right sides of the backrest of the driver's seat, l'l is a microcomputer, 12 is a bypass filter, and 13 is a calculation unit.

In the delay circuit 7, 21L and 21R are A/D converters, 22L and 22R are left and right channel delay units, and 23
L and 23R indicate D/A converters.

In addition, in the calculation unit 13, 24L, 24R, 25L,
25'R is an A/D conversion unit, 26L and 26R are cross-correlation function calculation units, 27L and 27R are maximum value detection units, 28 is left,
The right time difference calculation section is shown.

Figures 3 and 4 show the microcomputer 1 in Figure 1.
1 is a flowchart showing an example of processing in step 1.

In FIG. 1, left and right channel signals output from a sound reproduction device 6 such as a CD player are added to a delay circuit 7,
After converting into digital signals by A/D converters 21L and 21R and delaying them by delay units 22L and 22R, the D/A converter 2
3 L and 23R convert it again to an analog signal.

The output of the delay circuit 7 is branched into two, one (signal A) is inputted to the calculation unit 13 via the bypass filter 12, and the other (signal B) is passed through the switch circuit 8 and amplifiers 9L and 9R. , and is reproduced and output from the front speakers 1.2 and rear speakers (not shown) in the car. Further, the microcomputer 11 is connected to the delay circuit 7, the switch circuit 8, and the calculation section 13.

The operation of the present invention will be described below with reference to FIGS. 3 and 4, focusing on the processing performed by the microcomputer 11.

Turn on only one channel of the switch circuit 8, for example, the left channel (step 31), and from the brightness,
Output only one channel (left channel).

Determine the position of the listener's left and right ears from the headrest of the listening seat.
Of the two microphones 10L and IOR set nearby, the one closer to the output speaker, for example, the left microphone 10T, picks up the signal.

This signal B is passed through the bypass filter 12 to the calculation unit 1.
Enter 3.

In the calculation section 13, the A/D conversion sections 25L and 25R convert the signal B into a digital signal, which is input to the cross-correlation function calculation sections 26L and 26R. On the other hand, the output signal A of the delay circuit 7 is passed through the bypass filter 12, and the A/D converter 2
4- It is converted into a digital signal by L and 24R, and is input to the cross-correlation function calculating sections 26L and 26R.

The calculation units 26T, 26R calculate the cross-correlation of the signal B with respect to the signal A for each left and right channel (step 32).

A cross-correlation function is a function of the delay time obtained by examining the degree of similarity between two signals while changing the delay time of one signal. That is, the time when the cross-correlation function has the highest value is the time difference between the two signals. When applied to this system, the two signals are one channel of signal A and signal B. In order to increase the reliability of the time difference between the two signals determined from the cross-correlation function, a large number of averages are taken (step 33). Experiments have shown that a high degree of reliability can be obtained by taking the average of about 30 times.

Note that when the cross-correlation is expressed by a signal converted to discrete data, it becomes: rXy(■): Cross-correlation function xn: Input signal yn++n: Input signal (value shifted by m samples from n).

In this way, we calculate the average of the cross-correlation functions and use the result as
The maximum value detection units 27L and 27R are manually operated to find the time at which this average value reaches its maximum (step 34).

Reproduce the signal from the opposite channel, for example, the right channel speaker, pick up the sound with the microphone closer to the output of that speaker, for example, the right microphone, process it in the same way, and find the time at which the cross-correlation function reaches its maximum ( Steps (35-38
)).

The time output obtained by the maximum value detection section 27L, 27R is shown on the left.
The right time difference calculation unit 28 inputs the data to calculate the time difference between them (step 39).

FIG. 5 is a diagram for explaining an example of a method for calculating this time difference, in which (a) shows the cross-correlation function of the left channel, and (b) shows the cross-correlation function of the right channel. As can be seen from the figure, the time difference T corresponds to the difference between the time 1゛1 and T2 at which the cross-correlation functions in FIGS. 5(a) and 5(b) reach their maximum values,
-T, and outputs a signal corresponding to the time difference T to the microcomputer 11.

The microcomputer 11 controls the delay time of the delay circuit 7 using a delay control signal depending on the sign of the calculation result (step 40).

If the result is positive (plus), the right channel signal is delayed, and if the result is negative (minus), the left channel signal is delayed by time T (steps 41 and 42).

With this system, the output of the right channel speaker simultaneously reaches the right microphone, and the output of the left channel speaker simultaneously reaches the left microphone, eliminating the influence of the Haas effect. Even if the position of the seat or the angle of the backrest changes and the position of the listener's ears changes, the arrival time can be quickly corrected by operating this system.

Note that the two microphones are set near the left and right ears of the listener, for example, by arms from the headrest of the seat. This microphone is used only during measurement, and after the delay time is set, it can be stored in the headrest or removed.

In addition, the bypass filter 12 is designed to cut out the low frequency range in order to reduce the effects of engine noise, etc. Ideally, measurements should be taken in a noise-free location without applying a filter. good. Furthermore, the lower the cutoff frequency of the filter is, the higher the cross-correlation can be obtained. Set it to 1kHz or less at maximum. FIG. 6 shows an example of frequency characteristics of automobile engine noise.

After controlling the delay time of the delay circuit 7 using the delay control signal from the microcomputer 11, the left and right channels of the switch circuit 8 are turned on to perform normal playback (
Step 44).

According to the embodiment described above, there are the following features.

(1) Even if the listener moves the position of his or her head (ears) by changing the position of the seat or the angle of the backrest, the delay time of the delay circuit can be accurately corrected to be optimal for that position.

(2) Two microphones, one for the left ear and one for the right ear, are attached to the headrest of the seat for signal collection.

(3) Pick up the left channel speaker output with the left microphone and the right channel speaker output with the right microphone, and calculate the delay time of the delay circuit from the cross-correlation function between the signal and the left and right original signals. do.

(4) A bypass filter is provided to eliminate the influence of external noise (engine noise, etc.) during measurement.

(5) Since a normal music source is used as the measurement signal, there is no great burden on the listeners inside the vehicle.

In addition, although the above-mentioned embodiment described an example for use in a vehicle, the present invention is not limited thereto, and can also be used for home use.

[Effects of the Invention] As described above, according to the present invention, even if the position of the head (ears) of the listener moves by changing the position of the seat or the angle of the backrest, the position of the head (ears) will be optimal. This allows the delay time of the delay circuit to be quickly corrected.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the sound image localization control device according to the present invention, FIG. 2 is a diagram showing a general speaker arrangement and listening position, and FIGS. FIG. 5 is a flowchart showing an example of the processing, FIG. 5 is a diagram showing an example of delay time calculation, and FIG. 6 is a diagram showing an example of frequency characteristics of automobile engine noise. 1~4・・・・・・・・・Speaker, 7・・・・・・・・・
Delay circuit, 8...Switch circuit, 11...
・・・・・・Microcomputer, 12・・・・・・
. . . Bypass filter, 13 . . . Calculation section, 25 . . . Cross-correlation function calculation section, 2
6... Maximum value detection section, 27...
...Left and right time difference calculation section. Patent Applicant Clarion Co., Ltd. Agent Patent Attorney Nagai 1) Takeshi Part 3 Figure 4 [[End] Figure 4

Claims (1)

[Claims] a delay section that delays the left and right signals output from the acoustic source by delay times corresponding to the delay control signals; and a left section that is attached to the left and right sides, respectively, and that reproduces the left and right signals delayed by the delay sections. and right speaker,
A first cross-correlation function is calculated based on the left and right microphones placed on the left and right sides of the vicinity of the listener, respectively, and the delayed left signal and the signal from the left microphone, and the delayed a cross-correlation function calculating section that calculates a second cross-correlation function based on the right signal and the signal from the right microphone; and a first and second cross-correlation function calculating section that maximizes each of the first and second cross-correlation functions. a maximum value detection unit for determining the maximum value time;
1. A sound image localization control device comprising: a time difference calculation unit that calculates a difference between maximum time values; and a control unit that outputs the delay control signal based on the time difference.