JPS58200700A - Sound field correcting device - Google Patents

Abstract

PURPOSE:To obtain natural sound field, by inserting a delay circuit for correcting the difference of the distance from a receiving point to left and right speakers and a sound volume adjusting circuit for correcting the difference of sound strength to a signal circuit of the speakers in order to set the image in the center of right and left speakers when listening at asymmetrical position. CONSTITUTION:A delay circuit 26 for correcting the delay of sound propagation due to the difference of the distance from a listening point to a left speaker and right speaker is provided to a signal circuit which inputs a right channel signal out of a right channel input terminal Ri. An output corrected its propagation time due to the difference of the distance to the listening point by the circuit 26 is supplied to a sound volume adjuster 24 to correct the sound strength of the left and right speakers. A left channel signal out of a left channel input terminal Li is inputted to a left speaker 10 via a driving amplifier 22. A right channel signal corrected its sound propagation delay and sound strength by the circuit 26 and sound volume adjuster 24 is supplied to a right speaker 12 via a driving amplifier 20 so that the outputs of the amplifiers 20 and 22 become nearly equal, and the sound image comes to the center of the speakers 10 and 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sound field correction device for a stereo system that reproduces stereophonic sound by disposing left and right speakers.

In a stereo system, the left side as shown in Figure 1 (δ).

The standard condition is for the listener 14 to listen while being at a point equidistant from the right speaker 10. can be reproduced. For example, vocals are often configured with one singer in the center and instrument players around them, but when you play back such an original sound field and listen to it at a standard listening position, the sound image, especially when the singer is on the left and right speakers. It sounds like you're in the middle of the

However, in car stereos, the speakers can be installed on both sides of the vehicle interior, generally on both sides of the instrumental panel, and the listening position is limited to the driver's seat or passenger seat, and in either case, the standard speakers are biased to the left or right. It cannot be used as a listening position.

In the case of the driver's seat, it is close to the right speaker 12, so the
The sound image 16 appears to be located at the right speaker position. Two-channel stereos generally have a left and right balancer, and you can adjust this to strengthen the sound of the left speaker and weaken the sound of the right speaker to balance the sound of the left and right speakers. However, natural stereo playback sound cannot be obtained. That is, when the balancer begins to be adjusted as described above, the sound image certainly begins to move from the right speaker to the left speaker, but at a certain point the position becomes unstable. If you experiment with this with multiple people, they won't be able to come to a definitive conclusion, so they will point out random positions, and the results will vary.

The present invention aims to improve this point and localize the sound image to the center of the two left and right speakers even when listening to two-channel stereo in an asymmetrical position, making it possible to reproduce a natural sound field. .

The present invention is a sound field correction device for a stereo system having left and right speakers, which is inserted into the signal circuit of one of the left and right speakers to correct sound propagation delays due to the difference in distance from the listening point to the right speaker and the left speaker. A delay circuit compensates for the sound to reach the listening point at the same time, and corrects the difference in the strength of the sound from the left and right speakers due to the distance difference, so that the strength of the sound from both speakers is the same at the listening point. The present invention is characterized in that it is equipped with a volume adjuster for making the volume equal.Next, the details of this embodiment will be explained in detail.

FIG. 2 shows an embodiment of the present invention, in which 10.12 is the left and right speakers mentioned above, and 20.22 is an amplifier for driving them. Although these are already existing, in the present invention, a volume adjuster such as an attenuator 24 and a delay circuit 26 are inserted into the signal system of one speaker, the right channel speaker 12 in this example. The condition for the sound image to be localized near the center of the left and right speakers 10 and 12 is that the listener is located at a point equally distanced from the left and right speakers. However, the above condition is that the intensity of the sound from the left and right speakers 10 and 12 reaching the listener 14 is equal, and that the sound is transmitted from the left and right speakers. The present invention focuses on the fact that the required time (delay time) for the signal to reach the listener is equal, and that this can be done by signal processing.

The attenuator 24 is used to equalize the intensity of the sound from the left and right speakers heard by the listener, and the delay circuit 2
6 is designed so that the power j does not reach the listener through the left and right speakers, and the power j reaches the same point when the 6th sound reaches 0. The required delay time is the difference between the time t+ and t2 (t+-
t2), which is obtained by dividing the distance by the speed of sound, but according to experimental results, about 1 mS is sufficient for car stereos.

The attenuator 24 may have a level of about 5 dB. The attenuation amount of these attenuators and the delay time of the delay circuit need to be changed accordingly when the listener's position changes, but in a car stereo, the listener's position is fixed, such as when the driver is in the car. When installing, just set it to an appropriate value.

Note that if a switching circuit is provided and the attenuator 24 and delay circuit 26 are inserted into the left speaker channel,
You can listen to natural stereo playback sound from the passenger seat. To return to the standard style, circuits 24 and 26 may be shorted.

Further, the attenuator 24 may include left and right balancers.

A specific example is shown in FIG. Li is the right channel input end, L
i is the left channel input end. The amplifiers A1, A2 and the surrounding CR circuit constitute a low-pass filter LPF that allows only audible sounds to pass through, and the amplifier A31A4 and the surrounding CR circuit constitute a similar low-pass filter LPF. IC+
constitutes the aforementioned delay circuit 26 using a BBD (bucket brigade device) integrated circuit. IC2 is an integrated circuit that generates the clock required by the BBD, and consists of an oscillator O8C made up of two inverters and a peripheral CR circuit, and a buffer BUF made up of four inverters. The resistive voltage divider circuit at the output end of the latter-stage LPF constitutes the above-mentioned attenuator 24 that lowers the voltage by 5 dB. amplifier Aa,
Aa is a buffer for impedance conversion, and its output R
O and LO are on the left.

The signal is guided to the right channel amplifiers 20 and 22 to drive the speaker.

According to this invention, the sound from the left and right speakers is adjusted not only in intensity but also in delay time, making it possible to achieve natural stereo playback even when the listener is in an asymmetrical position away from the standard listening position. It is effective and applicable to stereo systems that target limited spaces such as indoors.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of stereo reproduction, FIGS. 11 and 2 are block diagrams showing an embodiment of the present invention, and FIG. 3 is a circuit diagram showing a specific example of the present invention. In the drawing, 10.12 are left and right speakers, 14 is listening point, 2
6 is a delay circuit, and 24 is a volume adjuster. Applicant: Minoru Aoyagi, Patent Attorney, Fujitsu Ten Co., Ltd.

Claims (1)

[Claims] In a sound field correction device for a stereo system that has left and right speakers, it is inserted into the signal circuit of one of the left and right speakers, and corrects the sound propagation delay due to the difference in distance from the listening point to the right speaker and the left speaker. A delay circuit ensures that the sound reaches the listening point at the same time, and a delay circuit corrects the difference in the strength of the sound from the left and right speakers due to the distance difference, so that the strength of the sound from both speakers is equal at the listening point. What is claimed is: 1. A sound field correction device comprising a volume adjuster for adjusting the volume of the sound.