JP2005151422A - Audio reproducing device and arrival time adjusting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable an arrival time to be adjusted as audio reproduction is made. <P>SOLUTION: Ultrasonic signals 5 of frequency f1 are superposed on audio signals supplied to a speaker 11 of a right channel, and ultrasonic signals 6 of frequency f2 are superposed on audio signals supplied to a speaker 12 of a left channel, A microphone 13 is provided at a listening position, and a time required for audio signals of each channel to arrive at the microphone 13 after they are emitted from each of the speakers 11 and 12 is obtained through a time alignment time calculation circuit 14. An arrival time difference between the audio signals of a right and a left channel is obtained through a time alignment control block 15. The time alignment control block 15 controls the delay times of variable delay circuits 3 and 4 so as to eliminate an arrival time difference. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an audio playback apparatus and an arrival time adjustment method that can always set an arrival time optimally in accordance with a listening position using ultrasonic waves.

  In general, when there are two speakers of an audio device, the optimum audio listening position is a position equidistant from the two speakers, that is, a vertex of an isosceles triangle having a straight line connecting the two speakers as a base. Is the ideal.

  However, in the audio playback device, the speaker that outputs the audio signal is not always set at an appropriate distance from the audio listener, and varies depending on the environment in which the audio device is installed. As a result, the left and right volume balance is lost, or the arrival time of sound waves from the left and right speakers is different. The difference in arrival time deteriorates the feeling of localization. Conventionally, an audio playback device that automatically adjusts the arrival time or volume of each speaker in accordance with the listening position has been proposed (see Patent Document 1).

Japanese Patent Laid-Open No. 11-331999

  In the conventional automatic adjustment system for the listening position, a test signal in the audible band is used, and as a preparation before audio reproduction, the test signal is reproduced and automatic adjustment is performed. However, even after automatic adjustment, the distance from each adjusted speaker deviates from the optimal point due to a slight movement of the listener or a change in the position of the head, and the system cannot always maintain the optimal point. When the listening position was changed, it was necessary to interrupt the playback of music, etc., play the test signal again, and redo the adjustment.

  Accordingly, an object of the present invention is to provide an audio playback device and an arrival time adjustment method capable of optimally setting an arrival time according to a listening position even during reproduction of an audio signal.

In order to solve the above-described problem, the present invention provides an audio reproducing apparatus for reproducing audio signals of at least two channels.
Adding means for superimposing an ultrasonic signal on the audio signal of each channel;
Variable delay means for delaying the audio signal of each channel;
At least two speakers to which an audio signal of each channel whose delay time is controlled by the variable delay means are respectively supplied while superposing the ultrasonic signal;
A microphone that is provided at a listening position and converts sound waves from a speaker into an electrical reproduction signal;
This is an audio playback device comprising control means for detecting the difference in arrival time from each of the speakers until reaching the microphone and controlling the delay time of the variable delay means so as to cancel the difference in arrival time.

The present invention relates to an arrival time adjusting method in an audio reproducing apparatus for reproducing audio signals of at least two channels.
An addition step of superimposing an ultrasonic signal on the audio signal of each channel;
A delay step for delaying the audio signal of each channel;
A reproduction step of reproducing the audio signal of each channel on which the ultrasonic signal is superimposed and the delay time is controlled by the variable delay means, respectively, on a speaker;
A signal detection step of converting a sound wave from a speaker into an electrical reproduction signal by a microphone provided at a listening position;
And a control step for controlling a delay time of the variable delay means so as to detect a difference in arrival time from each of the speakers until reaching the microphone and to cancel the difference in arrival time.

  According to the present invention, it is possible to always adjust the arrival time of the audio signal to the optimum one in accordance with the movement of the listening position even during reproduction of the audio signal.

  Hereinafter, an embodiment of the present invention in which a difference in sound wave arrival times of left and right channels is corrected will be described with reference to the drawings. The adjustment of the arrival time is referred to as time alignment. In one embodiment of the present invention, an audio signal and adjustment ultrasonic waves are emitted from a speaker during audio reproduction. FIG. 1 shows a signal spectrum of an audio signal to which adjustment ultrasonic waves are added. The vertical axis is the output level, and the horizontal axis is the frequency (unit: kHz). A broken line in FIG. 1 indicates a frequency of 20 kHz.

  In general, the frequency of the band (audible band) that a human can hear through hearing is said to be 20 Hz to 20 kHz. A frequency higher than this, that is, a frequency band of 20 kHz or more cannot be felt as a sound by humans and is called an ultrasonic wave.

  In FIG. 1, the signal spectrum of the audio signal is shown below 20 kHz (the left side of the broken line in FIG. 1). Further, f1 and f2 indicate the frequencies of ultrasonic signals used in one embodiment of the present invention. In this embodiment, as an example of the frequency of the ultrasonic signal, f1 is 25 kHz and f2 is 30 kHz. However, the frequency is not limited to these frequencies.

  Reference numeral 1 in FIG. 2 indicates the entire audio reproduction system according to the present invention. The audio reproducing apparatus used in the present invention is an audio reproducing apparatus that reproduces a tape recorder, a compact disc (CD, registered trademark) and the like. In this embodiment, the audio signal reproducing device is, for example, a CD player.

  Reference numeral 2 indicates an audio signal reproducing unit. The audio signal reproduction unit 2 performs the following signal processing. The presence or absence of a CD pit is detected by an optical pickup provided in the audio signal reproducing unit 2, and an RF signal is generated. The generated RF signal is demodulated by EFM (eight to fourteen modulation), subjected to error correction processing by CIRC (cross interleave Reed-Solomon code), and then D / A (Digital to Analog) converted. The analog audio signal obtained by the D / A conversion is supplied to the variable delay circuit 3 and the variable delay circuit 4 of the left and right channels.

In the adder circuit 7, the ultrasonic signal 5 having the frequency f <b> 1 is superimposed on the signal output from the variable delay circuit 3. The ultrasonic signal 5 is generated intermittently such that, for example, it continues for a predetermined time and then disappears for a predetermined time. An audio signal on which the ultrasonic signal 5 is superimposed is supplied to an output circuit 9 constituted by an audio amplifier or the like, and then supplied to a speaker 11 of a right channel (hereinafter referred to as RCH as appropriate). The audio signal and the ultrasonic signal 5 are simultaneously output from the speaker 11 when reproducing the audio signal. Further, the start time of each signal of the intermittent ultrasonic signal 5 superimposed on the audio signal is T _1R . T _1R is supplied to the time alignment time calculation circuit 14.

On the other hand, the same processing is performed on the audio signal supplied from the audio signal reproducing unit 2 to the variable delay circuit 4. That is, the intermittent ultrasonic signal 6 having the frequency f2 is superimposed on the audio signal output from the variable delay circuit 4 in the adder circuit 8. An audio signal on which the ultrasonic signal 6 is superimposed is supplied to a speaker 12 of a left channel (hereinafter referred to as LCH) via an output circuit 10 constituted by an audio amplifier or the like. An audio signal and an ultrasonic signal 6 are simultaneously output from the speaker 12 when the audio signal is reproduced. Also, the start time of each intermittent signal of the ultrasonic signal 6 superimposed on the audio signal is T _1L . T _1L is supplied to the time alignment time calculation circuit 14.

The microphone 13 is installed at a listening position or a position close thereto. The microphone 13 may be attached to headphones used by the listener. The ultrasonic signal 5 and the ultrasonic signal 6 which are output from the two speakers by the microphone 13 and arrived are detected. Further, the microphone 13 records the time when the ultrasonic signal 5 and the ultrasonic signal 6 are detected. Here, the time when the ultrasonic signal 5 is detected is T _2R, and the time when the ultrasonic signal 6 is detected is T _2L .

T _2R and T _2L recorded by the microphone 13 are supplied to the time alignment time calculation circuit 14. The time alignment time calculation circuit 14 calculates the arrival time T _2R -T _{1R of the} ultrasonic signal 5 from the RCH speaker 11 to the microphone 13. _Let T _R be the calculated arrival time. Similarly, the arrival time T _2L -T _1L of the ultrasonic signal 6 from the LCH speaker 12 to the microphone 13 is also calculated. Let the calculated arrival time be T _L. Since the frequencies of the ultrasonic signals 5 and 6 are different, the arrival time for each channel can be obtained.

Further, the time alignment time calculation circuit 14 calculates the distance between each speaker and the microphone 13 by multiplying the calculated arrival time T _R and the arrival time T _L by the speed of sound. Of the calculated distances, the distance from the RCH speaker 11 to the microphone 13 is D _R, and the distance from the LCH speaker 12 to the microphone 13 is D _L. In the case of T _L <T _R , D _R <D _L , in the case of T _L > T _R , D _R > D _L , and in the case of T _L = T _R , D _R = D _L Become.

Information relating to the distances D _R and D _L calculated by the time alignment time calculation circuit 14 is supplied to the time alignment control unit 15. The time alignment control unit 15 controls the delay time by the variable delay circuit 3 and the variable delay circuit 4 based on the information regarding the distances D _R and D _L.

As an example, the sound wave output simultaneously from the RCH speaker 11 and the LCH speaker 12 has a phase difference at the position of the microphone 13 due to the relationship D _R <D _L. This phase difference can be corrected by advancing the phase of the sound wave from the LCH speaker 12. However, it is easier to delay than to advance the phase of the signal.

Therefore, the time alignment control unit 15 performs the following control process. The signal supplied from the audio signal reproduction unit 2 to the variable delay circuit 4, that is, the phase of the sound wave output from the LCH speaker 12, is not delayed. On the other hand, the signal supplied from the audio signal reproduction unit 2 to the variable delay circuit 3, that is, the sound wave output from the RCH speaker 12 is delayed. Specifically, for example, assuming that the sampling frequency is F, the F is delayed by multiplying F by the above-described difference in calculation time (T _L −T _R ).

As described above, the microphone 13 is located at an equal distance from the RCH speaker 11 and the LCH speaker 12 by adjusting the delay time of the audio signals output from the two speaker RCH speakers 11 and the LCH speaker 12. And an ideal listening position can be secured. When T _L > T _R and D _R > D _L , the LCH audio signal is delayed by the variable delay circuit 4, and at the position of the microphone 13, D _R = D _L substantially. Is done.

  In the present invention, the ultrasonic signal 5 and the ultrasonic signal 6 are output from the two speakers even during reproduction of the audio signal. Therefore, even if the listening position (the position of the microphone 13) changes during playback of the audio signal, the delay time of the audio signal of each of the left and right channels is controlled in accordance with the changed listening position. There is no need to stop, and time alignment adjustment is always performed.

  The present invention is not limited to the above-described embodiment, and various modifications and applications are possible without departing from the gist of the present invention. In the above-described embodiment, two speakers are used. However, the present invention can also be applied to an audio system having three or more speakers. In that case, an ultrasonic signal having a frequency of 3 or more is superimposed on the audio signal of each channel.

  Further, in the above-described embodiment, the arrival time of the audio signal output from the speaker using the ultrasonic signal is set as the control target, but the volume balance output from the left and right speakers may be set as the control target.

  In the above-described embodiment, ultrasonic signals of different types corresponding to the number of speakers are prepared, and ultrasonic signals of different frequencies are output for each speaker. However, one type of ultrasonic signal is time-divisionally divided into each channel. It is also possible to output from each speaker by superimposing it on the audio signal.

It is a basic diagram which shows an example of the frequency spectrum of the audio signal in one Embodiment of this invention. 1 is a block diagram of an embodiment of an audio playback system according to the present invention. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Audio reproduction system 2 Audio signal reproduction | regeneration part 5, 6 Ultrasonic signal 7, 8 Adder circuit 11 Right channel (RCH) speaker 12 Left speaker (LCH) speaker 13 Microphone 14 Time alignment time calculation circuit 15 Time alignment control part

Claims (8)

In an audio playback device that plays back an audio signal of at least two channels,
Adding means for superimposing an ultrasonic signal on the audio signal of each channel;
Variable delay means for delaying the audio signal of each channel;
At least two speakers to which the ultrasonic signals are superimposed and the audio signals of the respective channels whose delay times are controlled by the variable delay means are respectively supplied;
A microphone that is provided at a listening position and converts sound waves from the speaker into an electrical reproduction signal;
An audio reproduction apparatus comprising: control means for detecting a difference in arrival time from each of the speakers until reaching the microphone and controlling a delay time of the variable delay means so as to cancel the difference in arrival time. In claim 1,
The audio reproduction apparatus, wherein the ultrasonic signal is a signal having a different frequency in each channel. In claim 1,
The above-mentioned ultrasonic signal is a signal having the same frequency and is superimposed on each channel in a time division manner. In claim 1,
The audio reproducing apparatus, wherein the control means obtains a difference between a start time of the ultrasonic signal and a detection time of the ultrasonic signal in the microphone as the arrival time. In an arrival time adjustment method in an audio reproducing apparatus for reproducing at least two channels of audio signals,
An addition step of superimposing an ultrasonic signal on the audio signal of each channel;
A delay step for delaying the audio signal of each channel;
A reproduction step of reproducing the audio signal of each channel on which the ultrasonic signal is superimposed and the delay time of which is controlled by the variable delay means using a speaker;
A signal detection step of converting a sound wave from the speaker into an electrical reproduction signal by a microphone provided at a listening position;
And a control step of controlling a delay time of the variable delay means so as to detect a difference in arrival time from each of the speakers to reach the microphone and cancel the difference in arrival time. In claim 5,
The arrival time adjustment method in which the ultrasonic signal is a signal having a different frequency in each channel. In claim 5,
The ultrasonic signal is a signal having the same frequency, and is an arrival time adjustment method that is superimposed on each channel in a time division manner. In claim 5,
In the control step, an arrival time adjustment method for obtaining a difference between a start time of the ultrasonic signal and a detection time of the ultrasonic signal in the microphone as the arrival time.

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