JPH04318898A - Coefficient setting method for reverberation addition device - Google Patents

Abstract

PURPOSE:To set a multiplication coefficient for removing an unpleasant sound generated at the tail part of reverberation as to comb filters which are connected in plural stages as to a sound field controller which adds the reverberation artificially to a musical sound signal, etc. CONSTITUTION:This reverberation addition device which has the comb filters connected in parallel and in the stages; and the respective comb filters are equalized in reverberation time by setting the multiplication coefficient of a multiplier so that gn=10<-3>D<n/>R<ev> and ReV=-3XD1/log10g1, where Dn is the delay time of an (n)th delay unit Dn and gn is the multiplication coefficient of the multiplier.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound field control device for artificially adding reverberation to music signals and the like. In particular, in the present invention,
The purpose of this study is to set multiplication coefficients for removing unpleasant sounds that occur at the rear of reverberation for multiple stages of comb filters connected in parallel.

0002

2. Description of the Related Art FIG. 4 is a diagram showing a conventional sound field control device. The sound field control device in this figure is a DSP (Digital S
ignal Processor), which reproduces the sense of presence and spaciousness of each music venue, such as a concert hall, live house, church, stadium, etc., and an initial delay memory 10 that preprocesses an input signal with a constant sampling period; a delay memory 20-1 that sequentially captures output data from the initial delay memory 10;
A non-recursive digital filter (FIR) consisting of a multiplier 20-2 that adjusts the amplitude of delayed data extracted from each tap of the multiplier 20-2 and an adder 20-3 that combines the output data from each multiplier 20-2. a delay device 30-1 that delays the output data from the initial delay memory 10 for a predetermined period of time, a multiplier 30-2 that adjusts the gain of the output of the delay device 30-1, and a multiplier 30-2 that adjusts the gain of the output of the delay device 30-1; Multiplier 30
-2 and the input data of the delay device 30-1; It includes an adder 40 that synthesizes the output data of the early reflected sound generation section 20.

The sampling frequency commonly used is 48
KHz, the maximum audible frequency is 20KHz
Approximately twice the amount of Delay device 30 of reverberation adding device 30
For example, a shift register, RAM, etc. are used for -1,
In the case of a shift register, the delay data is taken out from the output tap, and the delay time is set by selecting the output tap. In the case of RAM, the delay time is set via the memory address.

FIG. 5 is a diagram showing early reflected sounds and reverberant sounds formed by a sound field control device. As shown in this figure, the direct sound arriving directly from the sound source at the listener's seat is delayed by the initial delay memory 10 for T1 time, and the early reflected sound generator 20 reflects the direct sound from the walls, ceiling, floor, etc. An initial reflected sound is formed that arrives with a time delay corresponding to the longer distance than the direct sound.The initial delay memory 10 delays the direct sound by T2 time, and the reverberation adding device 30 repeats the reflection many more times to generate random sounds from all directions. A series of reverberant sounds are formed with a pattern in which the reverberations arrive at different times, with varying degrees of delay, and whose levels gradually attenuate.

FIG. 6 is a diagram showing a reverberation adding device consisting of four stages of comb filters. To simplify the description of the reverberation adding device shown in this figure, a multi-stage comb filter composed of four stages will be described. First, the configuration of this figure includes delayers 30-1, 31-1, 32-1, and 33-1, and multipliers 30-2, 31- as the first to fourth comb filters 30, 31, 32, and 33. 2, 32-2 and 33-2, adders 30-3, 31-3, 32-3 and 33-3,
Each delay device 30-1, 31-1, 32-1 and 33-1
includes an adder 34 that combines the outputs of the .

Comb filter (reverberation adding device 30) shown in FIG.
The reason for having multiple stages as shown in this figure is as follows. FIG. 7 is a diagram showing the frequency characteristics of the comb filter. This figure (
a) is the frequency characteristic of a single comb filter, and the tap Tap of the shift register is used as the delay time to form the sound field.
If data is extracted from the position of =4, that is, if the delay time is delayed by four times the sampling period, a peak will occur at a frequency position every fs/4. Since the frequency characteristics of a single comb filter are extremely poor as described above, a multi-stage configuration is used as follows.

[0007] Figure (b) shows the synthesized frequency characteristics of a four-stage comb filter, and since the peak frequency positions of each stage are shifted and synthesized, the frequency characteristics are flattened.

[0008]

[Problems to be Solved by the Invention] However, the following problems arose in the conventional reverberation adding device. Returning to FIG. 6, if a four-stage comb filter is used to improve such frequency characteristics, each delay device 30-1, 31-
The delay time of 1, 32-1 and 33-1 is D1, respectively.
, D2 , D3 and D4 as D1 > D2
Assume that there is a relationship of >D3 >D4. For simplicity of explanation, multipliers 30-2, 31-2, 32-2 and 33
-2 multiplication coefficients are g1, g2, g3 and g4, respectively, and the relationship is usually g1 = g2 = g3 = g4.

FIG. 8 is a diagram showing the reverberation time envelope of each comb filter. According to this figure, the decrease in amplitude increases as the delay time of each comb filter decreases, but in the post-reverberant envelope, the amplitude of the comb filter with a small delay time becomes too small and the impulse density decreases, so in the pre-reverberant envelope, the frequency characteristics change. Even though flattening has been achieved, there is a problem in that flattening cannot be achieved in the rear part of the reverberation. Therefore, when reverberating post-reverberation sound is reproduced, an unpleasant crackling sound tends to remain. Furthermore, there is another problem that if the delay times D1 to D4 can be set at the same time, the setting of the coefficients becomes easier overall.

[0010] Therefore, in view of the above problems, the present invention has the following features:
It is an object of the present invention to provide a coefficient setting method for a reverberation adding device that can easily flatten frequency characteristics even after reverberation.

[0011]

[Means for Solving the Problems] FIG. 1 is a diagram showing the basic configuration of the present invention. In order to solve the above-mentioned problems, the present invention provides a reverberation adding device having a plurality of stages of comb filters connected in parallel, where the delay time of the n-th delay device constituting each comb filter is Dn, and the multiplication coefficient of the multiplier is gn
, the multiplication coefficient of the multiplier is substantially gn
=10-3Dn/ReV, ReV =-3×D1/l
Set to og10 g1.

0012

[Operation] In the reverberation adding apparatus shown in FIG. 1, the multiplication coefficients for each multiplier of each of the comb filters are given by the above equations, so that the setting becomes easy. This setting allows
Since the reverberation time of each comb filter is the same, the envelopes of the reverberation characteristics match, and the frequency characteristics can be flattened in the post-reverberation region as well as in the pre-reverberation region. In other words, the reverberant density of the impulse can be kept almost constant even after the reverberation, and the density does not decrease as in the conventional case, making it difficult for unpleasant sounds to remain.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a diagram illustrating a method for setting coefficients of a reverberation adding device according to an embodiment of the present invention. To simplify the explanation, the configuration in this figure is substantially the same as that in FIG. It differs in that it is newly added.

A method for setting multiplication coefficients for each multiplier by the control unit 35 will be explained. Figure 3 is Figure 2
FIG. 2 is a diagram illustrating reverberation sound formation of one comb filter. As shown in the figure, if the delay time of this comb filter is D and the multiplication coefficient is g (g<1), and the level of the input signal is normalized to 1.0, the first reverberant sound is higher than the input signal. After a delay of D time, the amplitude becomes g, and the second reverberant sound is further delayed by D time, and the amplitude becomes g2, and so on.
The nth reverberation sound is nD time delayed from the input signal, and the amplitude is g
It becomes n. Here, if ReV is the reverberation time for the input signal to attenuate to -60 dB, then 20log10 g n
=20nlog10g=-60,ReV=nD(
sec), so ReV=-3×D/log10
g (sec).

[0015]Concert hall, live house, church,
The upper reverberation time ReV is determined based on the reverberation characteristics of a music venue such as a stadium, and based on this, the delay times D1 to D4 of each delay device in FIG. 2 and the multipliers 30-2 and 31- are determined.
2, 32-2, and 33-2, for example, the multiplication coefficient g1 of the multiplier 30-2. And for the multiplication coefficient gn of other multipliers 31-2, 32-2 and 33-2, gn = 10-3Dn/ReV(
n = 2, 3, 4). By determining the multiplication coefficients in this way, the comb filters 30, 31, 32 and 3
The reverberation time ReV of 3 becomes common, and the envelopes of the reverberation characteristics of each stage coexist in the post-reverberation part.

[0016] To explain using the specific numerical values shown in FIG. 2, D1 = 50ms, D2 = 45ms, D3 = 40
ms, D4 = 35ms, g1 = 0.7, then R
eV=-3×50ms/log10 0.7=970
msec, g2 = 10-3D2/970 = 0
．． 7254, g3 = 10-3D3/970 = 0.75
18,g4=10-3D4/970=0.7791 is obtained.

[0017] In general, the multiplication coefficient gn of a multiplier for an n-stage comb filter is gn = 10-3Dn/
Expressed as ReV. The characteristics of this multiplication coefficient setting are that the multiplication coefficient is increased as the delay time becomes smaller, the attenuation envelopes of each comb filter in the rear part of the reverberation are matched, and the reverberation density can be kept almost constant until the rear part.
5 can be set, making the setting easier.

As an additional embodiment, the control unit 35 sets the multiplication coefficient gk to gk = 10-3Dk/ReV for the k-th comb filter consisting of n-stage comb filters.
and set the slow 000 delay time Dk to Dk =
It may be set as D1/2(k-1)/n. By also setting this delay time Dk, the setting of the coefficients of the comb filter becomes easier overall. The setting of this delay time Dk, as shown in Fig. 7, makes the reference vibration peak frequencies of each comb filter equally spaced on the logarithmic axis, making it easy to flatten the combined frequency of the comb filter and optimizing the comb filter. do it like this.

[0019]

As explained above, according to the present invention, the n-th delay time of a plurality of parallel-connected comb filters is Dn, and the multiplication coefficient of the multiplier is gn = 10-3Dn.
/ReV,ReV =-3×D1 /log10 g1
Since the reverberation time of each comb filter can be made to match, unpleasant sounds are less likely to remain, and the coefficients can be easily set.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle configuration of the present invention.

FIG. 2 is a diagram illustrating a coefficient setting method of the reverberation adding device according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating reverberant sound formation of the first comb filter in FIG. 2;

FIG. 4 is a diagram showing a conventional sound field control device.

FIG. 5 is a diagram showing early reflected sounds and reverberant sounds formed by the sound field control device.

FIG. 6 is a diagram showing a reverberation adding device consisting of a four-stage comb filter.

FIG. 7 is a diagram showing frequency characteristics of a comb filter.

FIG. 8 is a diagram showing an envelope of reverberation time of each comb filter.

[Explanation of symbols]

30-1, 31-1, 32-1, 33-1...Delay device 30
-2, 31-2, 32-2, 33-2...multiplier 30-3
, 31-3, 32-3, 33-3...Adder 34...Adder 35...Control unit

Claims (1)

[Claims] 1. In a reverberation adding device having multiple stages of comb filters connected in parallel, where the delay time of the n-th delay device constituting each comb filter is Dn, and the multiplication coefficient of the multiplier is gn, The multiplication coefficient of the multiplier is substantially gn = 10-3Dn/ReV, ReV = -3
A method for setting coefficients of a reverberation adding device, characterized in that coefficients are set to ×D1 /log10 g1.