JPH0432600B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides an indirect sound generation device that can generate natural indirect sound having spatial characteristics by electrically processing an electric signal that does not include indirect sound components. Sound emitted into a space is reflected by reflective walls, ceilings, floors, ground, etc. around the sound source, and reaches the human ear. In other words, humans live in spaces where direct and indirect sounds exist, except for special rooms for experiments (anechoic chambers). Figure 1 shows the state in which direct sound 1 and indirect sound 2 exist in relation to their respective delay times and relative levels. Indirect sound 2 is the first reflected sound (also called early reflection sound) 3. and reverberation sound 4.
(Quoted from NHK Giken Monthly Report, April 1966 issue, "Problems with Adding Reverberation") The first reflected sound 3 is delayed by the direct sound 1.
The sound arrives after 30ms, and the second and subsequent reflected sounds cannot be perceived individually as reflected sounds, so any reflected sound after 50ms is considered to be reverberant sound. The above-mentioned first-order reflected sound is generated by being reflected from reflective objects existing around the sound source, so there is usually a plurality of first-order reflected sounds 3, not a single one, as shown in Figure 2. . Furthermore, it goes without saying that each primary reflected sound has various reflection directions. That is, by setting the conditions of the sound source, the listener, and the reflecting wall, it is possible to simulate an indirect sound model, and from that conclusion, it is possible to simulate a famous music hall. FIG. 3 shows a conventional example of a two-channel (2ch) reverberation adding device. Does not have indirect sound components
Add 2ch electrical signals to input terminals 1 ₁ and I ₂ , and connect each
After branching the signal to 0, add the signal at the same level to _0.
is generated and branched into two channels ₃ and ₄ via a time delay device 5 and a reverberation generator 6, a phase inverter 7 is inserted into one of them, and the signal is added to the original signal by adders 8 and 8'. Output from output terminals 0 ₁ and 0 ₂ . FIG. 4 shows the relationship between the delay time and relative level of the output signal of one of the output terminals of the conventional example shown in FIG. This shows that the reverberation sound 4 produced by the reverberation generator 6 is being generated with a time delay of . In this manner, in the conventional example, since no primary reflected sound is generated, natural indirect sound cannot be obtained. The present invention eliminates the above-mentioned conventional drawbacks, and provides a device that generates indirect sound with a strong natural feel by taking into account the spatial nature of the primary reflected sound. This is effective not only when playing back existing 2-channel sources. FIG. 5 shows actual measurement results of the relationship between the delay time and relative level of indirect sound in the room shown in FIG. 6. D is a direct sound, R ₁ to _{R 6} are indirect sounds, and Table 1 shows the incident angle with the front of the listener 20 being 0°.

[Table] In this way, the primary reflected sound has a delay time, a relative level, and an angle of incidence, and the above three conditions can be met using an electric circuit from an electric signal that does not have indirect sound components. If you generate an indirect sound that has the following characteristics, it will become a natural indirect sound. The present invention provides an indirect sound generating device that makes the delay time, relative level, and angle of incidence equivalent to those of natural indirect sound. FIG. 7 shows a speaker device that can make the user feel as if he or she is listening to the sound radiated from a speaker placed at point P while listening to the sound radiated from the speakers 10, 10'. In FIG. 7, H ₁₁ and H ₁₂ are transfer functions between the speakers 10 and 10' and the left and right ears of the listener 9, and
H〓 ₁ , H〓 ₂ are the transfer functions between the speaker and the left and right ears of the listener 9 when the speaker is placed at the point P, and are radiated from the speakers 10 and 10', and are transmitted to the left ear of the listener 9. - If the sound pressure applied to the right ear is equal to the sound pressure radiated from the speaker placed at point P and applied to the left and right ears of the listener 9, the listener 9 will hear the sound radiated from the speakers 10 and 10'. Even though the listener 9 is listening to the sound, a speaker is placed at point P, and the listener 9 feels as if he is listening to the sound from this speaker. Blocks 11 and 12 in FIG. 7 are front and rear setting circuits and binaural difference creation circuits to give the effect of placing a speaker at point P.
The characteristics of the front and rear setting circuit 11 are H ₁ /H ₁₁ , and the characteristics of the binaural difference generating circuit 12 are H ₁₁ ·H ₀₂ −H ₁₂ ·H ₀₁ /H ₁₁ ·H ₀₁ −H ₁₂ ·H ₀₂ . Regarding the above-mentioned front/rear setting circuit and binaural difference creation circuit, see, for example, Masatoshi Shinbo et al.'s "Directional Localization in Stereo Playback" Electroacoustic Research Committee material.
It is described in detail in EA 76-61 (1976), and will be summarized here. As shown in FIG. 17, in the case of two-speaker reproduction, there are four transfer functions between the two speakers and both ears. In normal stereo listening,
As shown in FIG. 18, symmetrical transfer functions are equal. As shown in Figure 16, if a sound source is located at the position of the sound image that should be localized at an arbitrary distance and direction, the sound pressure generated in the auditory canals of the left and right ears is
Let P _L and P _R be the transfer functions from the sound source to the left and right auditory canals as H ₀₁ and H ₀₂ . On the other hand, the playback speaker
Assume that the signal applied to SP.1 is E _L , the signal applied to speaker SP.2 is E _R , and the transfer function of the speaker is 1. Also, at this time, the sound pressures reproduced in the auditory canals of the left ear and right ear are assumed to be P _L ′ and P _R ′. Furthermore, the transfer function from speaker SP.1 to the left ear is H ₁₁ , and the transfer function to the right ear is H 11 .
H ₁₂ and the transfer functions for speaker SP.2 are defined as H ₂₁ and H ₂₂ in the same way. Here, below the sound pressure ratio of both ears P _R /P _L in Fig. 16b, P _R /P _L = H ₀₂ /H ₀₁ = A ... (1) P _r /P = H ₁₂ / H ₁₁ = B ... …(2) E _R /E _L =C …(3) The sound pressure ratio P _R ′/P _L ′ of the listener's both ears due to the reproduction speaker is P _R ′/P _L ′=H ₁₁・E _R +H ₁₂・E _R /H ₁₁・E _L +H ₁₂・E _L
=B・1+C/B/1+C・B……(4) Here, to find the reproduction speaker E _R /E _L required to make P _R /P _L and P _R ′/P _L ′ equal, , C=A-B/1-A・B=H ₁₁・H ₀₂ −H ₁₂・H ₀₁ /H _1
1・H ₀₁ −H ₁₂・H ₀₂ ...(5) This becomes the binaural difference generation circuit. To determine the direction of a sound source in all circumferential directions, in addition to the binaural ratio, a transfer function for front-back determination is required. 16th
Assuming the electrical input signal A _S in Figure b, the sound pressure P _L obtained at the listener's left ear is given by P _L =H ₀₁ ·A _S (6). on the other hand. The sound pressure P _L ′ obtained at the listener's left ear in Fig. 18 is P _L ′ = (H ₁₁・E _L +H ₁₂・E _R )・A _S ……(7) Here, P _L and P Finding the conditions to make _L ′ equal, H ₀₁・A _S =H ₁₁・E _L・(1+H ₁₂ /H ₁₁・E _R /E _L )・A _S
……(8) E _L =H ₀₁ /H ₁₁・1/1+(H ₁₂ /H ₁₁ )(E _R /E _L )≒
H ₀₁ /H ₁₁ ...(9) This is the front and back setting circuit. As described above, the sound image can be localized in the entire circumferential direction of the listener. FIG. 8 shows an embodiment of the present invention. In this embodiment, the signals applied to the input terminals I ₁ and I ₂ are each divided into two, and one of them is applied to the mixers 8 and 8'.
The remaining one is added at the same level, and this added signal
₁ is divided into a plurality of parts, each of which is applied to the primary reflected sound generation circuits a to m, and also applied to the reverberation sound generation circuit R. Each primary reflected sound generation circuit a~
m is the volume 1 for setting the relative level
3a to 13m, delay device 14a for setting delay time
~14m, and front and rear setting circuit 1 for setting the incident angle
1a to 11m and binaural difference generation circuits 12a to 12
m, each primary reflected sound generation circuit a to m
The outputs of are applied to mixers 8 and 8', respectively. The reverberation sound generation circuit R includes a volume 13n for setting the level and a delay device 14n for setting the delay time.
A reverberant sound signal generated by this reverberant sound generating circuit R is applied to mixers 8 and 8'. In the mixers 8 and 8', the direct sound signals from the input terminals I ₁ and I ₂ , the primary reflected sound signals from the primary reflected sound generating circuits a to m, and the primary reflected sound signals from the reverberant sound generating circuit R. are mixed with the reverberant sound signal and output to output terminals O ₁ and O ₂ . According to this embodiment, direct sound 1 in FIG.
Furthermore, it is possible to simulate a plurality of first-order reflected sounds 3 and reverberations 4, and to obtain natural indirect sounds. Note that in the above embodiment, the phase inverter 16
Alternatively, a time delay device having a delay time in the range of 10 ms to 50 ms may be used. The ninth example shows another embodiment of the present invention. In this embodiment, a plurality of primary reflected sound generating circuits a to m and a reverberant sound generating circuit R are provided, and the output of the reverberant sound generating circuit R is composed of a volume 13m, a time delay device 14m, and a reverberant sound generator 15. is branched and applied to the front stages of the front and rear setting circuits 11a to 11m of each of the primary reflected sound generation circuits a to m. Generally, primary reflected sound has directionality, but reverberant sound does not. For this reason, in FIGS. 8 and 9, front and rear setting circuits 11a to 11m and binaural difference generating circuits 12a to 12m are provided, and the first
The next reflected sound has directionality. In the embodiment shown in FIG. 8, a phase inverter 16 is provided in order to prevent reverberant sound from having directionality. The fact that reverberant sound has no directionality means that it does not have a specific directionality and is incident from all directions. For this reason, in the embodiment shown in FIG. 9, the reverberant sound signal is given a directionality set in each of the primary reflected sound generating circuits a to m. FIG. 10 shows yet another embodiment of the invention. In FIG. 10, 17 is a delay device 14a to
Divide each 14m output into 6 and connect 6 terminals r _1
6 -channel branch switching means 18 outputs to any terminal among terminals r 1 to r 6, and divides the signal obtained at each terminal r ₁ to _{r 6} into two, and is capable of changing the level ratio between these two outputs. This is a multi-channel pan pot that can be used. FIG. 11 shows the connection state of the 6-channel branch switching means 17 and the 2-channel panpot 18 connected to the output terminal of the delay device 14a in FIG. In FIG. 10, 19 and 19' are mixers. Outputs O ₁ and O ₂ in FIG. 10 are applied to speakers S ₁ and S ₂ in FIG. 12. Also, the front and back setting circuit 11a and the binaural difference creation circuit 1 in FIG.
2a localizes the virtual sound source S ₃ at 90 degrees to the right of the listener 19 in FIG. The virtual sound sources S ₄ , S ₅ , and S ₆ are localized in the left 90° direction, respectively, and by adjusting the 2-channel panpot 18, the sound source directions can be changed to, for example, the real sound source S ₁ and the imaginary sound source S in FIG. It is possible to localize in the P direction between . Similarly, by adjusting the two-channel panpot, the sound image can be localized in the range A to F shown in FIG. 12. FIGS. 13 to 15 each show still other embodiments of the present invention. In addition, Fig. 13-1
In FIG. 5, the same parts as in the previous embodiment are given the same numbers. The present invention has the above configuration, and according to the present invention, more natural indirect sounds can be generated.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing the relationship between delay time and relative level of direct sound and indirect sound, respectively. Figure 3 is a block diagram of a conventional reverberation adding device, and Figure 4 is a diagram showing the relationship between direct sound and indirect sound in the same device. Figure 5 is a diagram showing the relationship between delay time and relative level with indirect sound, Figure 5 is a diagram showing the relationship between delay time and relative level with direct sound and indirect sound in a given room, and Figure 6 is Figure 5. 7 is a diagram showing a block diagram of the main parts used in the device of the present invention. FIG. 8 is a block diagram of an indirect sound generator according to an embodiment of the present invention. 10 is a block diagram of another embodiment of the present invention, FIG. 11 is a block diagram of the main part of FIG. 10, FIG. 12 is a diagram showing the sound image localization direction in the apparatus of FIG. 10, and FIG. 15 are block diagrams of other embodiments of the present invention, and FIGS. 16 to 18 are block diagrams of other embodiments of the present invention, respectively.
The figure is a block diagram showing the principle of the front and back setting circuit and the binaural difference creation circuit. 8,8'...Mixer, 13a-13m...Volume, 14a-14m...Delay device, 11a-1
1m... front and rear setting circuit, 12a to 12m... binaural difference creation circuit, a to m... primary reflected sound generation circuit,
R... Reverberation sound generation circuit, 15... Reverberation sound generation circuit, 16... Phase inverter.

Claims (1)

[Claims] 1. A first branching means for branching an electrical signal that does not include an indirect sound component into a plurality of branches, a time delaying means for setting a delay time of each branched electrical signal, and a level variable means for setting the level of each branched electrical signal. Then, the transfer function from the sound source to the listener's left and right ear canals is expressed as H ₀₁ ,
Let H ₀₂ be the transfer function from one of the left and right speakers placed in front of the listener to the ear canal on the side closer to the listener's speaker, and H ₁₁ be the transfer function from the above speaker to the other ear canal of the listener. When is H ₁₂ ,
Input the above delayed and level-set signal,
A front and rear setting circuit that calculates H ₀₁ /H ₁₁ , a second branching means that branches the output signal into two, and one of the output signals of the second branching means as input (H ₁₁・H ₀₂ −
a binaural difference generation circuit that calculates H ₁₂・H ₀₁ )/(H ₁₁・H ₀₁ −H ₁₂・H ₀₂ ); a reverberation signal generation circuit that receives the output signal of the first branching means; A first adding means inputs the output signal of the first branching means, the other output signal of the second branching means, and the first output signal of the reverberation signal generation circuit; an indirect sound generating device comprising second adding means for inputting a second output signal of the reverberation signal generation circuit, an output signal of the binaural difference generation circuit, and a second output signal of the reverberation signal generation circuit.