JPS62163500A - Reververation unit for on-vehicle stereo acoustic device - Google Patents

Abstract

PURPOSE:To generate a reverberation sound having a natural expanding sense by one reverberation sound generating circuit, by making a reverberation sound signal which has been synthesized and generated from right and left channel signals, branch into two giving a level difference to the other signal, to one signal, and applying these signals to the original channels, respectively. CONSTITUTION:L and R channel signals which have been inputted to input terminals 1, 2 are added by an adding circuit 3, and thereafter, inputted to a reverberation sound generating circuit 4, and a delay processing is applied and a reverberation sound signal is generated. An output of the circuit 4 is made to branch into two, and one of them is added to the original L channel signal by an adding circuit 6, and the other is attenuated by 6-9dB by an attenuator, and thereafter, added by an adding circuit 7 to the R channel signal in which a transfer time difference of a sound by right and left loudspeakers and a level difference have been compensated by a delaying circuit 10 and an attenuator 11. Output signals from the circuit 6, 7 are outputted from output terminals 8, 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reverberation adding device used in a vehicle-mounted stereo sound device such as a vehicle-mounted tape stereo or a CD player. The reverberation adding device of the present invention is used to add reverberation sound to the output sounds of left and right channels to give a sense of spaciousness to stereo reproduced sound.

[Conventional technology]

Conventionally, in two-channel stereo sound equipment, in order to increase the sense of sound spaciousness during stereo playback, delay processing is added to the left and right channel signals (R) to create reverberation sound, which is then combined with the original channel signal. The same goes for in-vehicle stereo audio equipment.

The circuits shown in FIGS. 6 to 8 are conventional circuits for adding this reverberation sound. In the circuit shown in FIG. 6, reverberation sound generation circuits 4L and 4R are provided for both left and right channels, and the reverberation sound signals created by these circuits 4L and 4R are added to the left and right channel signals by adders 6' and 7, respectively, and converted to H. Adding.

The circuit shown in Fig. 7 combines left and right channel signals R in an adder circuit 3 (or subtracter circuit) and then leads them to a reverberation sound generation circuit 4, and adds the created reverberation sound signals to the left and right channels respectively. It is added to the signal R and R, thereby making the reverberation sound generation circuit into one.

Similar to the circuit shown in Fig. 7, the circuit shown in Fig. 8 synthesizes the left and right channel signals, R, in an adder circuit (or subtracter circuit) 3 and guides it to the reverberation sound generation circuit. One of the signals is sent directly to the adder 6, and the other is sent to the inverter 12.
After the phase is reversed, the signal is led to the adder 7.

[Problem that the invention seeks to solve]

In order to add reverberant sound to the left and right channels, it is originally desirable to create reverberant sound separately for each of the left and right channel signals.
As in the circuit shown in the figure, it is necessary to provide a reverberation sound generating circuit for each of the left and right channels. However, the reverberation sound generation circuit that can obtain natural reverberation sound has a relatively complicated and expensive configuration, so the need for two reverberation sound generation circuits means that the configuration is There are problems from the viewpoint of complexity and also from the viewpoint of cost.

In order to solve this problem, a reverberation addition circuit has been proposed, as shown in Figure 7, which eliminates one channel of the reverberation sound generation circuit by combining the left and right channel signals R and then guiding them to the reverberation sound generation circuit. Ru.

However, in this circuit, reverberant sound signals with the same signal level and the same phase are applied to the left and right channel signals, R, so the reverberant sound is localized in the center of the two speakers, resulting in a sense of spaciousness. cannot be obtained.

The circuit shown in Fig. 8 improves the shortcomings of the circuit shown in Fig. 5, and adds the reverberation sound signal to the left and right channel signals, R, in an antiphase relationship, and is commonly used. This is the way to be. This takes advantage of the fact that when an opposite-phase human signal is applied to the left and right channels, the position i6 of the sound image differs depending on the signal frequency, and therefore the sound image is not localized.However, when trying to emphasize reverberant sound, the opposite-phase There is a problem in that the sound is conspicuously audible, causing an audible discomfort.

Therefore, an object of the present invention is to provide a reverberation addition device for a vehicle stereo base device that can add reverberation sound with a natural sense of spaciousness while using a single reverberation sound generation circuit.

[Means for solving problems]

The present invention is based on the following findings.

In two-channel stereo reproduction, a phenomenon called the Haas effect is known. This Haas effect is a phenomenon in which a sound image that has been localized at the center of two speakers moves to the side of the channel that is not delayed by applying a delay to the signal of one channel.

Furthermore, in this state, if you reduce the signal level of the channel on the side where the sound image has moved, it is possible to return the sound image to the center and localize it, but the reason why this return to the center is possible is as described above. This phenomenon occurs only when the delay time applied to the channel signal is within a certain range, and this phenomenon is known as trading of the time difference and level difference between two signals.

Figure 3 shows the results of this trading experiment with the listening position set at the center of the two speakers in a vehicle.In the figure, the ordinate is the level difference (dB), and the abscissa is the time difference (μsec). shows. In addition, in the area indicated by diagonal lines, the evaluation of the sound image localization varies depending on the evaluator.
Therefore, the localization is not clear.

As is clear from the experimental results shown in Figure 3, if we consider that the range in which trading is possible based on the time difference and level difference between two signals in the vehicle interior is the range where the graph shows a monotonically increasing tendency, the delay time difference is approximately Up to 300μsec, and this 300μsec takes about 6d for trading.
Requires a level difference between B. The delay time difference is this 300μ
sec or more, it is no longer possible to return the sound image to the center due to the level difference between the two signals, the sound image spreads between the two speakers, and there is no sense of localization, and it is no longer clear from which position the sound is coming from. In other words, you can get a wide and angry sound.

By utilizing this phenomenon, it is possible to add two reverberant sound signals that satisfy the above conditions to the left and right channel signals, respectively, and generate reverberant sound with a more natural sense of spaciousness each time these signals are played back by the speakers. .

On the other hand, in a vehicle-mounted stereo sound device, two speakers are arranged, for example, on both sides of an instrumental panel, and are often asymmetrical with respect to the listener. FIG. 4 shows an example of the relationship between the front speaker systems placed on both sides of such an instrumental panel and the driver's seat as the listening position. In this example, the distance between the left speaker L on the far side from the driver's seat and the driver's seat is 112
cm, the distance between the right speaker on the near side and the driver's seat is 7
7cI11, and there is a distance difference of 35cm between them.

Therefore, even if the same sound is reproduced from two speakers, there will be a time difference of about 1 m5ec at the listening position.

Therefore, when the listening position is the driver's seat in the vehicle interior, the above-mentioned time difference condition is still satisfied. Therefore, it is possible to reproduce the above-mentioned non-localized sound with a sense of spaciousness through a speaker simply by providing a level difference condition.

Figure 5 shows the results of a localization experiment using level differences with the driver's seat inside the vehicle as the listening position.Vertical stranding is measured by relative level (dB), and horizontal stranding is measured by the distance of the listening position from the center of the vehicle (dB). am). As shown in the figure, in the driver's seat (approximately 40 C!l position on the right side), a level difference of 6 to 9 dB causes a point where the localization becomes unclear, ω, where a sense of sound spread is obtained. As mentioned above, this is due to the difference in sound transmission time from the two speakers to the driver's seat.

The reverberation adding device for a stereo audio system for a vehicle according to the present invention, which has been developed based on the above findings, is a stereo audio system for a vehicle that includes a speaker located far from a listener and a speaker located close to the listener. A synthesis circuit that synthesizes two channel signals, a reverberation sound creation circuit that creates a reverberation sound signal using the output signal of the synthesis circuit, and a reverberation sound generation circuit that branches the reverberation sound signal of the reverberation sound creation circuit into two paths. a level difference applying circuit that provides a level difference so that the reverberant sound signal of the first path has a higher signal level than the reverberant sound signal of the second path; and the reverberation of the first path of the level difference applying circuit. A first reverberant sound synthesis circuit that adds a sound signal to a channel signal of a speaker located far from the listener and outputs it as an output signal to the speaker, and reverberation in a second path of the level difference imparting circuit. A second reverberant sound synthesis circuit is provided which adds a sound signal to a channel signal of a speaker disposed close to a listener and outputs it as an output signal to the speaker.

[For production]

A synthesis circuit combines the left and right channel signals, and a reverberation sound generation circuit creates a reverberation sound signal.

Further, a level difference providing circuit divides this reverberant sound signal into two and provides a level difference between one signal and the other signal. This level difference is selected to a value such that the stereo reproduction of reverberant sound by the speakers does not have a sense of localization and appears wide and confusing. The two-branched reverberant sound signals are combined into original left and right channel signals by first and second reverberant sound synthesis circuits, respectively, and reproduced by speakers. Therefore, the reverberant sound has a sense of spaciousness without being localized.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a reverberation adding device for a stereo audio system as an embodiment of the present invention.

The listening position for this device is the driver's seat (right seat) inside the vehicle. In Figure 1, ■ and 2 are input terminals into which left and right channel signals are input, respectively, 3 is an adder circuit that adds the L channel signal and R channel signal, and 4 is a delay in the output signal of adder circuit 3. A reverberation sound generation circuit generates a reverberation sound signal by applying processing, and 5 is an attenuator that attenuates the reverberation sound signal, and in this example, it is configured to provide attenuation of 6 to 9 dB. 6 is the residual g sound signal of the reverberation sound generation circuit 4.

An adder circuit for adding the output signal of the attenuator 5 to the R channel signal; 8 an adder circuit for adding the output signal of the attenuator 5 to the R channel signal;
．． 9 is an output terminal for L and R channel signals to which reverberation has been added, respectively.

Note that 10 is a delay circuit, and 11 is an attenuator. The delay circuit 10 and the attenuator 11 are for correcting the sound transmission time difference and level difference caused by the distance difference between the left and right speakers, respectively, and each time the R channel signal is delayed and attenuated relative to the L channel signal. The right speaker is adjusted so that it is equivalently the same distance as the left speaker when viewed from the driver's seat, so that a central localization can be obtained for normal stereo signals.

An example of a detailed configuration of the reverberation sound generating circuit 4 is shown in FIG. In the figure, T'(1) is a high-pass filter, F(2)
is a bandpass filter, F(3) is a low-pass filter, D(1)
~D(5) are delay elements, A(1) to A(8) are adders, and M(1) to M(9) are coefficient units. Coefficient unit M (
The wave coefficient is written in each block of 11 to M(9), and g+ to g are approximately 0.9, and g4ngs is 0.
．． 7 was selected.

This reverberation sound generation circuit 4 filters the input signal by F (1)
~F(3) separates the frequency components into high, middle, and low frequency components and performs delay processing on each component, and then the adder A (
4) is synthesized again. In this delay processing, the input signal is delayed by the delay elements D(1) to D(3), and a part of the delayed output is sent to the coefficient multiplier M(11 to M(3)) and the adder A(1) to A(3). ) is fed back to the input terminals of delay elements D(1) to D(3), thereby creating a reverberant sound signal with a feeling of residual temperature.Output signal from adder A(4) further includes a processing circuit 4 called Schrader's system.
The density of the reverberant sound is determined each time it passes through L42 and is sent out from the output terminal.

The operation of the embodiment apparatus shown in FIG. 1 will be explained below.

The R and R channel signals inputted to the input terminals 1.2 are added by the adding circuit 3, and then inputted to the reverberant sound generating circuit 4, where they are subjected to delay processing, whereby a reverberant sound signal is created and output. This reverberant sound signal is branched into two, one of which is added to the original L channel signal in an adder 6, and the other is attenuated by 6 to 9 dB by passing through an attenuator 5, and then added to the original R channel signal in an adder 7. will be added. The output signal from the adder circuit 6.7 is output to the speaker and becomes an output sound.

The reverberant sound signal output from the reverberant sound generating circuit 4 is split into two, a level difference of about 6 to 9 dB is given between them, and added to the L and R channel signals, and the sound from the left and right speakers is Since there is a transmission time difference of approximately 1 m5ec in the driver's seat, the condition for eliminating localization described in +i is satisfied, and the reverberant sound reproduced has a natural sense of spaciousness without a sense of localization.

Various modifications are possible in carrying out the invention. For example, in addition to having a complex configuration as shown in Figure 2, a reverberation sound generation circuit is composed of a delay element to which a signal is input manually, and a feedback circuit that returns a part of the output of each delay element to the input side. It is also possible. In addition to the circuit in the embodiment, a circuit that gives a level difference between two reverberant sound signals can be used, for example, by amplifying one of the two branched reverberant sound signals and adding it to the channel signal of a distant speaker, and adding the other one directly to a nearby speaker. It may be a circuit configured to be added to a speaker channel signal. Furthermore, the circuit for combining left and right channel signals into one is not limited to the addition circuit 3 of the embodiment, but may be combined using, for example, a subtraction circuit. In this case, components of the left and right channel signals with the same level and phase are removed, and only components with different phases and levels between the left and right channels are output as reverberant sound. Further, in the above description, the driver's seat is set as the listening position, but it is of course possible to configure the apparatus with the passenger seat set as the listening position.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to realize the spread of natural stereo playback sound due to reverberant sound with a simple circuit configuration using only one reverberant sound generating circuit.
Helps simplify equipment and reduce costs. The device of the present invention has two
It is possible to obtain the same effect as a conventional device equipped with a channel reverberation sound addition circuit, and it is also possible to obtain an effect equivalent to that of a conventional device equipped with a channel reverberation sound addition circuit. The sound of the phase components is rarely heard and a natural sense of spaciousness can be obtained.

[Brief explanation of drawings]

FIG. 1 shows in-vehicle stereo sound 9 as an embodiment of the present invention.
A block diagram showing the reverberation adding device of the device, Fig. 2 is a detailed block diagram as an example of the reverberation sound generating circuit shown in Fig. 1, and Fig. 3 shows the 1-rating of the time difference and level difference between two signals. Figure 4 is a diagram showing the experimental results. Figure 4 is a diagram explaining the arrangement of the vehicle-mounted front speaker system. Figure 5 is a diagram showing a sound image localization experiment using volume differences. Figures 6 to 8 are conventional reverberation sounds. FIG. 3 is a block diagram showing each additional device.

Claims (1)

[Scope of Claims] 1. A synthesis circuit for synthesizing two channel signals in an in-vehicle stereo audio system comprising a speaker disposed far from a listener and a speaker disposed close to the listener; A reverberant sound generation circuit that creates a reverberant sound signal using an output signal of a synthesis circuit;
a level difference providing circuit that provides a level difference so that the reverberant sound signal on the second path has a higher signal level than the reverberant sound signal on the second path; a first reverberant sound synthesis circuit that outputs an output signal to the speaker in addition to a channel signal from a speaker located far from the listener; and a reverberant sound signal on a second path of the level difference imparting circuit. A reverberation adding device for a vehicle-mounted stereo audio system, comprising: a second reverberation sound synthesis circuit which adds a channel signal of a speaker disposed close to a listener to an output signal to the speaker. 2. The device according to claim 1, wherein the arrival time difference between the output sounds of the two speakers at the listener's position is at least 300 milliseconds or more. 3. The device according to claim 1 or 2, wherein the level difference applying circuit comprises an attenuation circuit inserted in the second path. 4. The device according to claim 1 or 2, wherein the first level difference applying circuit comprises an amplifier circuit inserted in the first path. 5. The signal level difference imparted by the level difference imparting circuit is selected to a value such that the stereo reproduction of reverberant sound by the speakers does not have a sense of localization.
Apparatus according to any of paragraph 4. 6. The device according to any one of claims 1 to 5, wherein the synthesis circuit is comprised of either an addition circuit or a subtraction circuit. 7. Claims in which the reverberation sound generation circuit includes a delay circuit that delays an input signal, and a feedback circuit that feeds back a part of the output signal of the delay circuit to the input side of the delay circuit. The device according to any one of items 1 to 6. 8. The device according to any one of claims 1 to 7, wherein the listener's position is a driver's seat of a vehicle.