JPH03959B2 - - Google Patents

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 the left and right channels to give a sense of spaciousness to stereo reproduced sound.

[Prior Art] Traditionally, two-channel stereo sound equipment has created reverberation by adding delay processing to the left and right channel signals L and R, with the aim of increasing the sense of sound spaciousness during stereo playback. is added to the original channel signals L and R, and the same is true for car stereo sound 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 L and R by adders 6 and 7, respectively. ing.

In the circuit shown in FIG. 7, left and right channel signals L and R are combined in an adder circuit 3 (or subtracter circuit) and then guided to a reverberant sound generating circuit 4, and the created reverberant sound signals are sent to left and right channels in adders 6 and 7, respectively. Channel signal L, R
In addition to this, the reverberation sound generation circuit is integrated into one.

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

[Problem that the invention seeks to solve]

To add reverberation to the left and right channels,
Originally, it is desirable to create reverberation sounds separately for each of the left and right channel signals L and R, and for this purpose, a reverberation sound generation circuit is provided for each of the left and right channels, as shown in the circuit shown in Figure 6. It is necessary to provide however,
A reverberant sound generating circuit that can produce natural reverberant sound has a relatively complex and expensive configuration, so the need for two reverberant sound generating circuits is disadvantageous from the perspective of complicating the configuration. However, there are also problems from a cost perspective.

In order to solve this problem, a reverberation addition circuit has been proposed, as shown in Fig. 7, in which the left and right channel signals L and R are combined and then guided to the reverberation sound generation circuit, thereby omitting one channel of the reverberation sound generation circuit. Ru.
However, in this circuit, the reverberant sound signals of the same signal level and the same phase are transmitted to the left and right channel signals L and R.
Since the reverberant sound is applied to the center of the two speakers, the reverberant sound is located in the center of the two speakers, making it impossible to obtain a sense of sound spread.

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 L and R in an antiphase relationship, and is commonly used. This is the way to be. This takes advantage of the fact that when input signals of opposite phase are applied to the left and right channels, the position of the sound image differs depending on the signal frequency, and therefore the sound image is not localized.
If an attempt is made to emphasize the reverberant sound, there is a problem in that the sound with the opposite phase becomes conspicuous and audible, resulting in an audible sense of discomfort.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a reverberation addition device for a vehicle-mounted stereo audio system 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 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 signal on the side where the sound image has moved, it is possible to return the sound image to the center and localize it.
This return to the center is possible only when the delay time applied to the channel signal described above is within a certain range, and this phenomenon is known as trading of the time difference and level difference between the two signals.

Figure 3 shows the results of a 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. Furthermore, the width area indicated by diagonal lines is a range in which the evaluation of the localization of the sound image varies depending on the evaluator, and therefore the localization is not perfect.

As is clear from the experimental results shown in Figure 3,
Considering that the range in which trading is possible due to the time difference and level difference between two signals in the vehicle interior is the range in which the graph shows a monotonous increasing trend, the delay time difference is up to about 300 μsec, and at this 300 μsec, trading is approximately 6 dB. requires a level difference. When the delay time difference exceeds this 300μsec, it is no longer 2
Due to the level difference between the signals, it becomes impossible to return the sound image to the center, and the sound image spreads between the two speakers, causing a loss of localization and making it unclear where the sound is coming from. In other words, a sense of spaciousness of the sound can be obtained.

By utilizing this phenomenon, it is possible to generate reverberant sound with a natural sense of spaciousness by adding two reverberant sound signals that satisfy the above conditions to the left and right channel signals and reproducing them through 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 arranged 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 side farthest 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 77
cm, and there is a distance difference of 35 cm between them.

Therefore, even if the same sound is played from two speakers, there will be a time difference of about 1 msec at the listening position. Therefore, if the listening position is the driver's seat inside the vehicle,
Even as it is, the above-mentioned time difference condition is 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 in the vehicle as the listening position.Vertical stranding is measured by the relative level (dB), and horizontal stranding is measured by the distance of the listening position from the center of the vehicle (dB). cm). As shown in the figure, in the driver's seat (approximately 40 cm to the right), there are places where the localization becomes unclear due to a level difference of 6 to 9 dB, and here a sense of spaciousness of the sound can be 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 combination circuit that combines two channel signals, a reverberation sound creation circuit that creates a reverberation sound signal using the output signal of the combination circuit, and a reverberation sound signal of the reverberation sound creation circuit that is split 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 of a second channel 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 near a listener and outputs the signal to the speaker.

[Effect]

The left and right channel signals are combined by a synthesis circuit, and a reverberation sound signal is further created by a reverberation sound generation circuit. Further, a level difference providing circuit branches this reverberant sound signal into two and provides one signal with a certain level difference with respect to the other signal. This level difference is selected to a value such that the stereo reproduction of reverberant sound by the speakers has no sense of localization and appears to be spread out. 2
The 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 that cannot be localized.

〔Example〕

Embodiments of the present invention will be described below 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, 1 and 2 are input terminals into which the left and right L and R channel signals are respectively input, 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 reverberant sound signal of the reverberant sound generating circuit 4.
An adder circuit 7 adds the output signal of the attenuator 5 to the R channel signal, and 8 and 9 are output terminals for the 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 due to the distance difference between the left and right speakers, respectively.
By delaying and attenuating the R channel signal relative to the L channel signal, the right speaker is adjusted to be equivalently the same distance as the left speaker when viewed from the driver's seat, and the center position is adjusted for normal stereo signals. It is intended to be obtained.

An example of a detailed configuration of the reverberation sound generating circuit 4 is shown in FIG. In the figure, F1 is a high-pass filter,
2 is a band filter, F3 is a low pass filter, D1~
D5 is a delay element, A1 to A8 are adders, M1 to M
9 is a coefficient unit. Subtraction coefficients are written in each block of coefficient multipliers M1 to M9, and g ₁ to
g ₃ is selected to be approximately 0.9, and g ₄ and g ₅ are selected to be 0.7.

This reverberation sound generation circuit 4 passes the input signal through a filter F.
The frequency components are divided into high, middle, and low frequency components at F1 to F3, and after delay processing is performed on each component, they are combined again at adder A4. In this delay processing, the input signal is delayed by the delay elements D1 to D3, and a part of the delayed output is fed back to the input side of the delay elements D1 to D3 by the coefficient multipliers M1 to M3 and the adders A1 to A3. This creates a reverberant sound signal with a sense of reverberation. The output signal from the adder A4 further passes through processing circuits 41 and 42 called a Schrader system to determine the density of reverberant sound and is sent out from an output terminal.

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

The L and R channel signals input to input terminals 1 and 2 are added by an adder circuit 3, and then input into a reverberation sound generation circuit 4 and subjected to delay processing, whereby a reverberation sound signal is created and output. This reverberant sound signal is split into two branches, one of which is sent to the adder circuit 6 to return the original L signal.
It is added to the channel signal, and the other one is attenuated by 6 to 9 dB by passing through the attenuator 5 and then sent to the adding circuit 7.
is added to the original R channel signal. The output signals from the adder circuits 6 and 7 are output to the speaker and become 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 msec at the driver's seat, the above-mentioned condition for eliminating localization is met, 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 generating circuit may be configured with a delay element into which a signal is input, and a feedback circuit that returns part of the output of this delay element to the input side. 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. Further, 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 sense of spaciousness of natural stereo playback sound due to reverberant sound with a simple circuit configuration using only one reverberant sound generating circuit, which simplifies the device. , helps reduce costs. The device of the present invention can obtain the same effect as a conventional device equipped with a two-channel reverberation sound addition circuit, and also converts the conventional one-channel reverberant sound signal into the original signal in reverse phase. Compared to the splitting method, you hear less of the out-of-phase component, and a natural sense of spaciousness can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a reverberation adding device for a vehicle-mounted stereo audio system as an embodiment of the present invention;
Figure 2 is a detailed block diagram of an example of the reverberation sound generation circuit shown in Figure 1, Figure 3 is a diagram showing experimental results of trading the time difference and level difference between two signals, and Figure 4 is for automotive use. FIG. 5 is a diagram illustrating the arrangement of the front speaker system, FIG. 5 is a diagram illustrating a sound image localization experiment based on volume differences, and FIGS. 6 to 8 are block diagrams illustrating conventional reverberation sound adding devices. 1, 2... Input terminal, 3... Addition circuit, 4... Reverberation sound generation circuit, 5... Attenuator, 6, 7... Addition circuit, 8,
9...Output terminal.

Claims (1)

[Scope of Claims] 1. A synthesis circuit for synthesizing two channel signals in a vehicle-mounted stereo audio system including 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 circuit, a reverberant sound signal of the reverberant sound generator circuit is branched into two paths, and the reverberant sound signal of the first path is the reverberant sound of the second path. A level difference applying circuit that applies a level difference to the signal so that the signal level becomes larger; and a channel on the speaker side disposed far from the listener for transmitting the reverberant sound signal of the first path of the level difference applying circuit. a first reverberant sound synthesis circuit that outputs the reverberant sound signal in addition to the signal as an output signal to the speaker, and a reverberant sound signal on the second path of the level difference imparting circuit to the speaker side located near the listener. A reverberation adding device for an in-vehicle stereo audio system, comprising: a second reverberation sound synthesis circuit that outputs a signal to a speaker in addition to a channel signal. 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 second level difference providing circuit comprises an amplifier circuit inserted in the first path. 5. The signal level difference provided in the level difference providing circuit is selected to a value such that the stereo reproduction of reverberant sound by the speakers does not have a sense of localization. The equipment described in section. 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. The reverberant sound generating 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 the driver's seat of a vehicle.