JPS6060074B2 - Reverberation adding device - Google Patents

Description

Detailed Description of the Invention The present invention calculates an autocorrelation function of an input signal, calculates an autocorrelation coefficient at a certain delay time, and calculates an autocorrelation coefficient at a certain delay time in a reverberation adding circuit of a stereo device, a karaoke device, etc. The present invention provides a reverberation addition device that produces an optimal reverberation effect corresponding to an input signal by changing the amount of feedback of a delayed signal of a reverberation addition circuit in accordance with the magnitude of an autocorrelation coefficient.

Conventionally, the delay time or level ratio of the reverberation adding circuit is changed depending on the level of the input signal, and the delay time of the reverberation adding circuit is changed depending on the magnitude of the autocorrelation coefficient at a certain delay time of the input signal. There are things that make you do it.

Among the factors that confuse people about reverberation, the delay time and the amount of feedback of the delayed signal have a large effect on the sound quality of reverberation.

Furthermore, it is well known that the physical characteristics of a sound source signal can be quantified by an autocorrelation function, and it has been reported that reverberation is related to the autocorrelation function of a sound source in subjective evaluation in a sound field. The autocorrelation function of a sound source generally shows a tendency as shown in FIG.

The autocorrelation coefficient at the current delay time Tl is determined. If the coefficient is large, the correlation with the original signal is high, so the reverberation is increased accordingly. Conversely, if the coefficient is small, the correlation with the original signal is low, so the reverberation is reduced. Changing the reverberation addition amount in accordance with the magnitude of the correlation coefficient in this way has physical meaning, and may be used as a reverberation effect. FIG. 1 shows a general reverberation adding circuit. Input signal 1 enters adder 6 as direct sound signal 2. At the same time, the delayed signal 3 that has passed through the delay circuit 7 is sent to the attenuator 9, and the delayed signal 3 passes through the attenuator 8 and is applied to the adder 5 for feedback. The direct sound signal 2 and the delayed signal 4 that has passed through the attenuator 9 are added by an adder 6 to obtain an output signal 10 with added reverberation. In the present invention, as shown in FIG. 2, the autocorrelation coefficient calculation circuit 11 calculates the autocorrelation coefficient of the input signal 1, and changes the amount of attenuation of the attenuator 8 depending on the magnitude of the autocorrelation coefficient.

FIG. 3a shows an example of the autocorrelation coefficient calculation circuit 11.

The autocorrelation coefficient at a certain delay time Tl of the input signal is determined by multiplying the direct sound signal 2 by the delayed signal 17 passed through the delay circuit 14 in a multiplier 13, and averaging the result in an averaging circuit 15. If multiple delay times are required due to the characteristics of the input signal,
As shown in the figure, τ1, τ2...γ. , and find the autocorrelation coefficient for each. The magnitude of the autocorrelation coefficient of the input signal thus obtained is computed by the arithmetic circuit 16 and converted into a feedback amount control signal voltage 12 corresponding to the magnitude. In the arithmetic circuit 16,
A1 added value, B1 average value, C1 peak value, D1 weight added value, etc. are calculated. Also, the time constant L of the averaging circuit 15
−. are the characteristics of the input signal and the delay circuits τ1 to τ. It is determined by the value of . As mentioned above, Fig. 3a shows an example of an analog autocorrelation coefficient calculation circuit, but there is also a unipolar autocorrelation method in which only one of the direct sound signal 2 and the delayed signal 17 is made into a zero-crossing wave. Number calculation circuit, 2,
This can be realized using a bipolar autocorrelation coefficient calculation circuit as shown in FIG. 3b, or even a digital computer. In FIG. 3b, 18 is a zero-cross wave forming circuit, and 19 is a logic circuit.

FIG. 5 shows an example of the relationship between the magnitude of the autocorrelation coefficient of the sound source and the feedback amount of the reverberation adding circuit.

FIG. 5 a1 A case where the magnitude of the autocorrelation coefficient of the sound source and the amount of feedback correspond in a linear relationship as shown in y1. Figure 5b
The magnitude of the autocorrelation coefficient of one sound source and the amount of feedback are Y
When dealing with a non-build relationship like in 2.

This is a case where the magnitude of the autocorrelation coefficient of the C1 sound source in FIG. 5 and the amount of feedback correspond linearly up to the magnitude of the coefficient φ1 and in a nonlinear relationship beyond that, as shown in Y3.

In actual use, it is most effective to use a nonlinear correspondence like Y2.

The reverberation adding device of the present invention has the above-described configuration, and when the device of the present invention is used in a reverberation adding circuit of a stereo or karaoke device, a large amount of reverberation is generated in areas where the autocorrelation coefficient of the input signal is large. It has the advantage that a small amount of reverberation is automatically added where the correlation coefficient is small, creating a reverberation effect that is more comfortable for both the singer and the listener than a constant amount of reverberation. This is something that can be obtained.

Brief description of the drawings Fig. 1 is a block diagram of a conventional reverberation adding device, Fig. 2 is a block diagram of a reverberation adding device according to an embodiment of the present invention, and Fig. 3 A and b show respective autocorrelation coefficient calculations. A block diagram of the circuit, FIG. 4 shows an example of the autocorrelation coefficient of a sound source, and FIGS. 5A, b, and c show the relationship between the magnitude of the autocorrelation coefficient and the amount of feedback in the reverberation adding device of the present invention, respectively. FIG.

1... Input signal, 2... Direct sound signal, 3... Delayed signal, 4... Delayed signal, 5, 6... Adder, 7...
・Delay circuit, 81. --Attenuator, 39: Attenuator, 10: Output signal, 11: Autocorrelation coefficient calculation circuit.

Claims (1)

[Claims] 1. In a reverberation adding device that delays an input signal via a delay circuit and feeds back this delayed signal to the delay circuit via an attenuator to generate reverberated sound, the autocorrelation coefficient of the input signal is calculated by autocorrelation. The attenuation amount of the attenuator is controlled according to the magnitude of the autocorrelation coefficient at one point or multiple points on the time axis of the autocorrelation function by calculating with a numerical calculation circuit, and the amount of feedback of the delayed signal is changed. Characteristic reverberation adding device.