JPH0729600U - Reverberation device - Google Patents

Abstract

(57) [Summary] [Purpose] To generate a natural reverberation sound with a simple structure in which the density of the reverberation signal increases over time. [Structure] The input signal is a delay circuit 34 having a delay time τ1.
Is input to the comb filter 48. The feedback path 46 of the comb filter 48 has a delay time of τ2 (τ2 <τ
The all-pass filter 52 having the delay circuit 62 of 1) is inserted. The reverberation signal is output from a tap in the middle of the delay circuit 34.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a reverberation adding device that artificially adds reverberation using a comb filter, and is capable of generating a natural reverberation with a simple structure in which the density of the reverberation increases with time. It was done.

[0002]

[Prior art]

 As a device for artificially adding reverberation, a device using a comb filter has been generally used. For example, as shown in FIG. 2, this is composed of a signal path 10 through which an acoustic signal passes, a delay circuit 12, a feedback path 14 having an amplifier 13 with a gain smaller than 1, and an adder 16. In this configuration, a reverberation signal of the input signal is obtained at the output side by repeatedly attenuating the input signal while repeatedly circulating the input signal.

In order to obtain a natural reverberation sound in the reverberation adding device, a certain density is required between the reverberation signal generation intervals. In the comb filter 11 of FIG. 2, the generation time of the reverberation signal can be increased by shortening the delay time τ1 of the delay circuit 12. However, in the comb filter, sharp peaks appear at an interval of 1 / τ 1 on the frequency-amplitude characteristics, so if the delay time τ 1 is shortened, the intervals between peak positions will widen, and the peaks will be conspicuous to give an unnatural sound. Therefore, there is a limit even if the delay time τ is shortened. Also, the natural reverberation has a higher density of reverberant sound over time, but in the comb filter 11 of FIG. 2, the reverberant signal is obtained only at a constant time interval τ 1, and the initial reflected sound If τ1 = 30 ms is set for the purpose of expression, it is not possible to express a sufficient diffused state in the reverberant sound (late reflected sound).

Therefore, as a means for solving the drawback while using the comb filter, the reverberation adding device 20 shown in FIG. 3 has been considered. This is an arrangement in which an all-pass filter (all-pass filter) 22 is arranged after the comb filter 11 shown in FIG. Many reverberation signals can be produced by circulating the reverberation signal produced by the comb filter 11 in the loop 26 including the delay circuit 24 and the amplifier 25 having the gain g. Then, by making the delay time τ2 of the delay circuit 24 shorter than the delay time τ1 of the delay circuit 12 of the comb filter 11, the reverberation signal density can be increased. Therefore, the delay time .tau.1 of the delay circuit 12 of the comb filter 11 can be set to be relatively long, whereby the interval between peak positions on the frequency-amplitude characteristic can be shortened to make the peak inconspicuous. The all-pass filter 22 itself can keep the frequency-amplitude characteristic flat even if the delay time τ2 of the delay circuit 24 is shortened.

Further, according to the reverberation adding device 20 of FIG. 3, since the reverberation signal is further generated by the all-pass filter 22 on the basis of each reverberation signal generated by the comb filter 11, the reverberation signal generation density with time. Can be increased.

[0006]

[Problems to be solved by the device]

 In the reverberation adding device of FIG. 3, since the all-pass filter 22 has only one stage, if the feedback gain (amplifier 25) of the all-pass filter 22 is made too large, the reverberation signal generation density will increase too much from the beginning. However, on the contrary, if the feedback gain is reduced, the feeling that the reverberation signal generation density increases with time cannot be fully expressed. In order to increase the generation density of the reverberation signal with a natural feeling over time and to obtain a practically sufficient diffusion of the reverberation sound, the all-pass filters 22 must be connected in multiple stages as shown in FIG. There is a drawback that the circuit scale becomes large.

The present invention solves the above-mentioned problems in the conventional technique, and in a reverberation adding device using a comb filter, a reverberation sound having a natural feeling in which the density of the reverberation signal increases with time is simplified. An object of the present invention is to provide a reverberation adding device that can be generated with a configuration.

[0008]

[Means for Solving the Problems]

 According to the reverberation adding device of the first aspect, the all-pass filter is inserted in the loop of the comb filter.

In the reverberation adding device according to the second aspect, a plurality of circuits having all-pass filters inserted in the loop of the comb filter are connected in parallel, and the delay times of the delay circuits of the comb filters are different from each other. It is set to a value.

[0010]

[Action]

 According to the invention of claim 1, since the all-pass filter is inserted in the loop of the comb filter, the reverberation signal generated by the all-pass filter is repeatedly circulated in the loop of the comb filter. , The density of the reverberation signal can be increased with the passage of time. Therefore, it is possible to obtain practically sufficient diffusion of reverberation sound with a simple configuration.

According to the second aspect of the present invention, a plurality of circuits having an all-pass filter inserted in the loop of the comb filter are connected in parallel, and the delay times of the delay circuits of the comb filters are different from each other. Since the value is set to a value, it is possible to cancel the frequency characteristic of the comb filter and to bring it closer to a flat characteristic when it is necessary to reduce the comb characteristic.

[0012]

【Example】

 An embodiment of the invention described in claim 1 is shown in FIG. The input audio signal is input from the input terminal 30 and input to the delay circuit 34 via the adder 32. The delay circuit 34 is composed of an analog delay circuit such as BBD or CCD for analog input, and is composed of a digital delay circuit such as delay memory for digital input. The delay time of the delay circuit 34 is set to τ1 (for example, 30 to 100 ms) as a whole, and the left and right output signals are taken out from the taps τL and τR in the middle thereof. By using different taps on the left and right sides, there is a slight time difference between the left and right sounds, which gives a stereo effect. The tap position at which the output is taken out is variably controlled by the output taking-out tap control means 36 based on the operator's instruction or the like. As a result, the delay time of the reflected sound at the beginning changes, and the sense of listening position can be changed even in the same sound field. The left and right output signals extracted from the delay circuit 34 are led to the output terminals 42 and 44 via the amplifiers 38 and 40.

The signal delayed by τ1 in the delay circuit 34 is fed back to the adder 32 via a feedback path 46 that forms a loop 50, and thus forms a comb filter 48. An all-pass filter 52, a filter circuit 54, and an amplifier 56 are arranged in the return path 46. The signal input to the all-pass filter 52 is input to the adder 60 via the amplifier 58 having a gain of g. Further, this input signal is delayed by τ2 (for example, a delay time of about 1/10 to ¼ of τ1) by a delay circuit 62 via an adder 68, and then passed through an amplifier 64 having a gain of 1-g ^2. Is input to the adder 60. The output of the delay circuit 62 is fed back to the adder 68 via the amplifier 66 having a gain of -g. The adder 60 adds the outputs of the amplifiers 58 and 64 and outputs the added value to the return path 46 of the comb filter 48 as the output signal of the all-pass filter 52. The filter circuit 54 provided in the return path 46 represents the attenuation of sound propagating in the air and the material of the wall. Further, the gain G1 of the amplifier 56 is set to a value such that the overall gain of the feedback path 46 is 1 or less.

According to the above configuration, the input signal is delayed by τL and τR in the delay circuit 34 of the comb filter 48 and is output, and becomes the first reflected sound. The signal delayed by τ1 in the delay circuit 34 is input to the all-pass filter 52 and a reverberation signal is generated in a period of τ2. Each reverberation signal generated by the all-pass filter 52 is returned to the delay circuit 34 of the comb filter 34 after being G1 attenuated by the amplifier 56, and after being delayed by τ1, input to the all-pass filter 52 again, based on each reverberation signal. Further, a reverberation signal is generated. As described above, according to the reverberation adding device 70 of FIG. 1, a reverberation signal whose generation density increases with the passage of time can be obtained.

FIG. 5 shows the waveform of each part when an impulse signal is input to the circuit of FIG. In FIG. 5, (a) is the input impulse signal, (b) is the signal at point a in FIG. 1, and (c) is the signal at point b. According to (c), it can be seen that the initial reflected sound is obtained and the reverberant sound whose density increases with the passage of time is also obtained.

In this case, in order to increase the reverberation signal generation density with time in a more natural manner, the delay time τ2 of the delay circuit 62 of the all-pass filter 52 is set to be greater than the delay time τ1 of the delay circuit 34 of the comb filter 48. It is effective to set the feedback gain -g (amplifier 66) of the all-pass filter 52 small (to bring g close to zero) while making it sufficiently short. Since the all-pass filter 52 is repeatedly used on the loop 50 even if the feedback gain is reduced, the final reverberation signal generation density is set to the upper limit value of the reflected sound density determined by the delay time τ2 of the all-pass filter 52. It gradually increases, and the process of the increase changes from a state in which the reflected sound is sparse to a audible and natural feeling.

FIG. 6 shows an embodiment of the invention according to claim 2. The reverberation adding device 72 is formed by arranging a plurality of the reverberation adding devices 70 of FIG. 1 in parallel and combining the outputs of the reverberation adding devices 70 for the left and right channels by adders 74 and 76. In each reverberation adding device 70, the delay time τ1 of the delay circuit 34 of the comb filter 48 is different from each other. As a result, the overall density of the reverberation can be increased, and the frequency characteristics of the comb filter can be canceled to make the characteristics closer to flat. By making the delay time τ2 of the delay circuit 62 of the all-pass filter 52 different from each other, the reverberation sound can be generated more randomly.

The comb filter and the all-pass filter according to the present invention are not limited to the configuration shown in FIG. 1 and various configurations can be used.

[0019]

[Effect of device]

 As described above, according to the invention of claim 1, since the all-pass filter is inserted in the loop of the comb filter, the reverberation signal generated by the all-pass filter repeats the loop of the comb filter. It becomes circular, and the density of the reverberation signal can be naturally increased over time. Therefore, it is possible to obtain practically sufficient diffusion of reverberation sound with a simple configuration.

According to the second aspect of the present invention, a plurality of circuits having the all-pass filter inserted in the loop of the comb filter are connected in parallel, and the delay times of the delay circuits of the comb filters are different from each other. Since the value is set to a value, it is possible to cancel the frequency characteristic of the comb filter and to bring it closer to a flat characteristic when it is necessary to reduce the comb characteristic.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the device according to claim 1.

FIG. 2 is a circuit diagram showing a conventional comb filter.

FIG. 3 is a circuit diagram showing a conventional reverberation adding device in which an all-pass filter is provided after the comb filter.

FIG. 4 is a circuit diagram showing a reverberation adding device in which the all-pass filters of FIG. 3 are arranged in multiple stages.

5 is a waveform diagram of each part when an impulse signal is input to the reverberation applying apparatus of FIG.

FIG. 6 is a circuit diagram showing an embodiment of the invention according to claim 2.

[Explanation of symbols]

 48 Comb filter 50 Comb filter loop 52 All-pass filter 70, 72 Reverberation device

Claims (2)

[Scope of utility model registration request] 1. A reverberation adding device in which an all-pass filter is inserted in a loop of a comb filter. 2. A reverberation adding device in which a plurality of circuits each having an all-pass filter inserted in a loop of a comb filter are connected in parallel and delay times of delay circuits of the comb filters are set to mutually different values. .