JPH0119155B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that electronically adds artificial reverberation to an acoustic signal, and provides a device that can add more natural-looking reverberation by controlling its temporal envelope. This is what I am trying to do.

First, FIG. 1 shows the basic configuration of a conventionally used delay circuit for adding a reverberation signal. Here, 1 is the input terminal of the input signal, 2 is the delay circuit τ
delay element, 3 is β times (however, |β|<1)
4 is a synthesis circuit, and 5 is an output terminal for an output signal.

FIG. 2 shows how the envelope of the output signal changes when an input signal of an impulse response with a positive magnitude of 1 is applied to this circuit. However, this is for the case where β is positive. In this way, the envelope change of the output signal is This results in a monotonically attenuating signal.

Next, we will introduce an example of a conventional reverberation adding circuit in which these basic circuits are combined with different delay times.
As shown in FIGS.

The circuit shown in FIG. 3 has a structure in which the basic delay circuits shown in FIG. 1 are connected in series, and the circuit in FIG. 5 has a structure in which they are connected in parallel. 6 is an output synthesis circuit. The change state of the envelope of the output signal for the positive impulse response of each circuit is
As shown in FIG. In this way, in order to complicate the signal delay time and make the reverberation signal more effective, delay circuits with different delay times were conventionally constructed by combining them. The envelope of the monotonically decaying waveform corresponding to the delay circuit appears as it is in the output signal. Therefore, in a combination of delay circuits equipped with feedback circuits having different delay times, the envelope of the output signal can be controlled arbitrarily. That was impossible.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a device that can arbitrarily control the envelope of an output signal, which has been a drawback of the conventional devices as described above.

First, we will discuss the necessity of controlling the envelope of the output signal.

In order to create a natural sound in a sound reproduction device,
It is sufficient to add reverberation sound that simulates a time-series envelope change with respect to the impulse response of an actual sound field. However, the conventional structure described above uses a completely omnidirectional sound source and merely simulates a sound field in which the reflection from the walls of the reproduction room is uniform. In other words, it was assumed that the magnitude of the reflected sound obtained at the listening point was determined only by the length of the path taken by the reflected sound (that is, the magnitude of the delay time). However, since such a sound field does not exist in reality, only reverberant sound with an unnatural feel could be obtained.

However, in a real sound field, the sound source (for example, a speaker) has directionality, and the reflectance of walls, etc. is not uniform, so reflected sound with a long delay time is more sensitive than reflected sound with a short delay time. There are also cases where the level of is large. In other words, it sounds more natural when the envelope of the reflected sound is not monotonically attenuated.

Therefore, the present invention allows the change in the envelope of this output signal to be arbitrarily controlled using a delay element having a single delay time, and will be described below along with embodiments.

The embodiment shown in FIG. 7 uses two delay elements 2a and 2b with the same delay time τ, and adds feedback circuits 3a and 3b with different feedback coefficients β _a and β _b , respectively.
The configuration is such that each output signal code is combined with different weights (here, 1 and -1). 6b is an inverter that inverts the sign.

In this device, when an input signal with a positive impulse response waveform of magnitude 1 is applied to input terminal 1,
At the output end of the delay element 2a, an output signal with a time-series envelope change as shown in FIG. 8 is obtained.
At the output terminal of the inverter 6b, an output signal with a time-series envelope change as shown in FIG. An output signal of envelope change is obtained. In this way, with this circuit, the rising portion of the output signal is smoothed, and a reverberation signal that reaches its maximum value and then decays smoothly again can be obtained.

That is, the envelope y _a of the output signal of delay element 2 is The envelope −y _b of the output signal of the inverter 6b is given by Therefore, the envelope g of the output signal that is synthesized by the synthesis circuit 6 and appears at the input terminal 7 is It will be given by

Therefore, the maximum value of this envelope characteristic
q _M and its time t _M are the case where the differential of the envelope change is 0, and since q = 0, t _M = log (β _a / β _b ) (log β _b / log β _a ) 〓 +
When τ, q _M = β _a log (β _a / β _b ) (log β _b / log β _a ) − β _b log
(β _a /β _b ) (logβ _b /logβ _a ). However, in Figures 9 and 10, 0<β _b <
Illustrated as β _a <1.

By appropriately selecting β _a and β _b in this way,
t _M and q _M can be arbitrarily selected.

Another embodiment is shown in FIG. The configuration shown in FIG. 11 is a general extension of the configuration shown in FIG. 7, and includes n delay elements 2 having the same delay time τ.
It is constructed using a, 2b...2n.
3a, 3b...3n are respective delay elements 2a, 2b
. . . 2n is a feedback circuit that performs feedback with different feedback coefficients β _a , β _b . . . β _o , 4 a, 4 b .
2b...2n is a circuit that applies different weights k ₁ to k _o including their signs, and 6 is a combining circuit consisting of an adder.

With this configuration, β _a , β _b ... β _o and k _a , k _b ...
By arbitrarily setting k _o , the time-series envelope change of the output signal appearing at the output terminal 5 when an impulse response input signal is applied to the input terminal 1 can be made into an arbitrary shape. For example, the first
It can also be done as shown in Figure 2.

Therefore, a circuit with the configuration shown in Fig. 11 is used as a unit in place of the conventional basic circuit shown in Fig. 1, and delay circuits with different delay times are connected vertically as shown in Figs. 3 and 4. By connecting them in parallel, it is possible to obtain an output with added reverberant sound that has a natural reverberant feel that could not be obtained conventionally.

As described above, according to the present invention, since the feedback circuits are connected in parallel, the signal circulates, so that a long reverberation sound can be obtained with a small number of delay elements, and the reverberation sound signal to be added is It is possible to obtain a useful device that can arbitrarily control the change state of the envelope and add natural-looking reverberant sound.

[Brief explanation of drawings]

Fig. 1 is a basic configuration diagram of a conventional delay circuit, Fig. 2 is a characteristic diagram showing envelope changes of its output signal, Fig. 3 is a configuration diagram of a reverberation adding device in which conventional basic delay circuits are connected in series, Figure 4 is a characteristic diagram showing the envelope change of the output signal, Figure 5 is a configuration diagram of a reverberation adding device in which conventional basic delay circuits are connected in parallel, Figure 6 is a characteristic diagram showing the envelope change of the output signal, and Figure 6 is a characteristic diagram showing the envelope change of the output signal. Figure 7 is a configuration diagram of a reverberation adding device in one embodiment of the present invention, Figures 8, 9, and 10.
Figure 11 is a characteristic diagram showing the envelope change of the output signal, Figure 11 is a configuration diagram of a reverberation adding device in another embodiment of the present invention, and Figure 12 is a characteristic diagram showing an example of the envelope change of the output signal. . 1...Input terminal, 2, 2a, 2b...2n...
Delay element, 3, 3a, 3b... 3n... feedback circuit, 4, 4a, 4b... 4n, 6... synthesis circuit,
5... Output terminal, 6a, 6b...6n... Weighting circuit.

Claims (1)

[Claims] 1 A plurality of delay circuits are configured such that feedback circuits with different feedback coefficients are connected in parallel to each of a plurality of delay elements having the same delay time, and a common 1. A reverberation adding apparatus characterized in that an input signal is added, and the output signals of each of the plurality of delay circuits are added with different weights, including signs, to produce an output signal.