JPS58194500A - Zooming device of audio signal - Google Patents

Abstract

PURPOSE:To obtain the feeling for distance of a sound image and furthermore to secure an impression to hear the sound at a place extremely close to the head of a listener even though the sound source exists just in front of the listener, by branching a monophonic sound source signal into two parts so as to obtain a phase difference of pi/2 radian. CONSTITUTION:A monophonic sound source S supplies a monophonic sound source signal to a 90 deg. phase shift circuit P'. The two output signals delivered from the circuit P' have a phase difference of about pi/2 radian along almost entire audible frequency band. One of these two output signals is supplied to a speaker SP1 via variable attenuators A4 and A6 and reproduced in the form of a signal of the left channel. While the other output signal is led to a variable attenuator A1, and furthermore the remaining branched output signal is led to a variable attenuator A3 after the polarity is inverted by a polarity inverter I. The other output signal of the circuit P' is led to a variable attenuator A2. The output signals of attenuators A1-A3 are mixed with each other and supplied to a speaker SP2 via attenuators A5 and A7 to be reproduced in the form of a signal of the right channel. In such a way, the distance feeling can be obtained for a sound image.

Description

[Detailed Description of the Invention] Regarding the digital signal zooming device, in particular, it is capable of continuously changing the sense of distance of sound from the feeling of being heard far away to the feeling of being heard very close to the listener. It is.

Generally speaking, in the production of a single stereo broadcast, the sound 1 has the function of arbitrarily determining the horizontal footing of the sound, or expressing the effect of horizontal movement, that is, panning.
& Foot positioning devices are used.

On the other hand, perspective control, that is, the effect of zooming, has only been realized in a very narrow and limited range, as described below, and a dedicated device for this purpose has not been put to practical use.

The audio signal zooming device # is a sound image localization device in the far and near direction that provides a zooming effect of 4 compared to the conventional sound image localization device # in the left and right directions that gives a panning effect. It has a wide range of applications as an effect device for program production.

In stereo playback, we get the psychological impression that each sound source, such as the sound of an instrument, a person's voice, or a sound, exists in each position within the 9-space, and the image of each sound source is formed into an f-image. It is called the continuous control of the perspective of this sound image.
Control methods that have traditionally been used as needed in drama programs include (1) changing the volume, (C) changing the amount of reverberation, (J) changing the frequency characteristics, etc. It is common to use control methods and combinations of these control methods.
Although these control methods can produce a certain effect, they cannot form a sound impression tube close to the line connecting one speaker! (There was a problem.

Regarding the conventional sound image perspective control as described above, the configuration and operation of the device, as well as problems, drawbacks, etc., will be explained in further detail.

In stereo reproduction, the following methods are theoretically known as methods for forming a sound image very close to the listener.

In other words, when the sound source is diagonally in front of the listener, diagonally behind the listener, or in a certain lateral direction, the sound U that enters both ears
, has a constant interaural phase difference and an interaural level difference that are determined according to the direction 1 of the sound source, and the direction of the sound source is perceived using such phase difference and level difference as clues.

On the other hand, Nakazai, Nikaido, and Mori's paper ``An experiment on the ability to discriminate sound source distance'' (Collection of Lectures by the Phonetic Society of Japan, 1932)
According to K, when the distance of the scale is within about 1 meter, even if the direction of the sound source is constant, due to the influence of the 7 (B) fold by the head, The interaural phase difference and the interaural level difference change depending on the distance lkK of the sound source, and these points serve as clues to distinguish the difference in the distance between the sound sources. Taking advantage of this phenomenon, if we perform a simulation in which one stereo left and right signal is processed so that equal binaural phase differences and binaural level differences occur when a sound source is located at a short distance, it is possible to It is thought that the impression of a distant sound source can be formed. However, in principle, this method will not have the desired effect unless the sound is listened to at a strictly defined listening position in a room with very little residual noise. First, if you try to continuously change the sense of distance for any material sound, you will need an extremely complex simulation, which is not easy to achieve.Furthermore, the effect of sound diffraction due to the head As for the sound source in the front direction, it is equal for both ears, so the above-mentioned phase difference and level difference do not occur. It is theoretically impossible to control the sense of distance using this method.In addition, as a study from a completely different perspective from the above, there is a paper by Kurozumi and Ogushi [The quality of sound images in Kotjanners Bika playback]. ” (Proceedings of the Aesthetic Society of Japan, July 1939, p. 439), using - mutually independent noise generators, the correlation coefficient between the signals reproduced from the left and right speakers is calculated. From 7 to 0, further K, and θ to -7, from left and right in phase to left and right independent and uncorrelated.
Furthermore, as K changes from uncorrelated to left and right opposite phase,
The sense of distance of the sound image changes from far (to near), and the correlation coefficient is -7
It has been reported that in some cases, it can be felt very close to the head. In other words, the sound that is applied to the listener's ears when left-right out-of-phase sound is not necessarily physically equal to the sound when listening to a nearby sound source, but it may give a subjective impression of being similar. It is clear from the above-mentioned literature that

Although the distance sense of the K1-1 sound image can be changed in principle by the above-mentioned method, the method according to the above-mentioned literature is applicable in that it requires seven pairs of stereo signals that are most strictly independent of each other. There is an essential problem that the range of the sound source is extremely narrow, and in addition, the correlation coefficient is close to θ, giving the impression that it has spread significantly. Therefore, when a single sound source moves from far to near, It is impossible to create a feeling of coming.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned various conventional problems, to obtain a sense of distance of a sound image even when the sound source is in the front direction, and to be closer than the line connecting the number of reproduction speakers.
It is possible to give an impression very close to the listener's head, and the single sound source does not spread from far to near.
It is an object of the present invention to provide an audio signal zooming gear that provides a sense of movement.

That is, the audio signal zooming device gt of the present invention includes a means for splitting a monophonic sound source signal, and a means for splitting a monophonic sound source signal into two parts over almost the entire audible frequency band. 9, comprising means for forming a one-branch signal by continuously changing it to an arbitrary desired value; and means for performing audio signal zooming using the co-branch signal as left and right signals of a stereo sound source. .
(The present invention will be described in detail below with reference to the drawings.

First, the basic structure of the audio signal zooming device of the present invention is shown in the first ryJK. , phase shift circuit P
The monophonic sound source signal is supplied to the speaker S, and after controlling the phase difference between the phase q output signals of the phase shift circuit P by the control circuit C, the phase shift output signals are supplied to the speaker S.
It is supplied to P1 and SF3 and generated as left and right signals of a stereo sound source.

Control of the phase difference between the phase-shifted output signals described above is performed according to the operating principle shown in FIG. In other words, the horizontal axis in Figure 1 is a scale that indicates the sense of distance of the sound image. For example, assume that the control knob has a scale that indicates force and force. Indicates a far state "far", and in that state, the phase difference between the output signals of the phase shift circuit P becomes a value close to θ or FiOK over the entire range of the possible@1IIJ wavenumber band. . The right end of the distance sense scale described above indicates the state in which the sense of distance is closest, ``Near'', and in state II, the phase difference between the output signals of BJ #! Therefore, 1-1 has a value of π radian or close to π radian over the entire range. Furthermore, in the middle of this distance scale, the phase difference between the phase-shifted output signals at each frequency is, for example, Or, as shown in #i curve B, the pressure is continuously changed monotonically.This straight HA or curve B does not necessarily have to be equal at each frequency, but if it is made equal at each frequency, KFi% When the correlation coefficient between the two output signals is close to zero, that is, when there is no correlation, the resulting musical temperament can be further concentrated.

A phase shift circuit having the above-mentioned phase difference characteristics [ol circuit f:
Considering the correlation coefficient between the signals of both systems, we find that when the distance scale is in the "far J" state, the correlation coefficient #'! is 1, and in the "near" state, it is #1 - l. , the value in between changes continuously. Therefore, the sense of distance of the sound image can be continuously changed from far away to near the listener's head. The moving speed of the sound source follows the change in the phase difference mentioned above, so it can be changed according to the speed of movement of the control knob of control circuit C.Next, use a %90 phase shift circuit. A specific example of the configuration of the audio signal zooming device of the present invention is shown in FIG.

Here, the a output signals from the 9θ0 phase shift circuit P' cover almost the entire audible frequency band and are t! It has a phase difference of π/coradian. One of the output signals is branched into three, and one of the branch output signals is sent to variable attenuators A4 and A4.
4 f through speaker 8Pt K, left channel (
or right channel) signal. Another branch output signal is guided to a variable attenuator A1, and the polarity of the remaining branch output signal is inverted by a polarity inverter l, and then guided to a variable attenuator MLK. In addition, to phase shift circuit P'
The other output signal of the output signal is led to a variable attenuator A2K. The output signals of these variable attenuators Az, At, and Am are mixed with each other and sent to speaker SP2 via variable attenuators AI and A7.
K is supplied and reproduced as a right channel (or left channel) signal. In addition, variable attenuators A1, A2, As, A4
, As, A4, and AxFi, respectively, are connected in series 11, and the relationship between their functions and attenuation amounts is determined as follows.

That is, the variable attenuators A1, A2, A11j are interlocked variable attenuators for continuously changing the phase difference between the outputs of the speakers SP1 and SF3 from 0 to radian. Its transmission amplitude characteristics are of the type (A), (BIK), and type (2), and have the characteristics shown in Table 1 below.

Table 1 Transmission amplitude characteristics of variable attenuators A1, A2, AM When the scale (θ) of the variable attenuators is 0, both speakers SP
1. Phase difference #i between the outputs of SF3.

When the scale θ is K, which is the state of the farthest sense of distance, the phase difference between the outputs of both speakers SP1 and SF3 is π radian, and the closest distances M and I are
Enters IA state 〇Variable attenuator A4, AIFi This is a type of variable attenuator conventionally used as an inverse movement type variable attenuator to change the position of the sound image left and right. The amount of attenuation of both is changed in a complementary manner so that the amount of attenuation is always constant. Generally in the vicinity of # = x/, -,
The sound gjIFi is slightly biased towards the speaker of the channel whose phase is leading, so I used variable attenuator A4. Al1
Fi is used as necessary to correct the bias in sound localization.

Furthermore, the variable attenuators A6 and A7 are interlocking type variable attenuators with the same percentage, which have been commonly used in the past. In other words, in general, when the sound source is far away, the volume will be low, so the amount of attenuation is maximized near θ = 0, and θ = π
The amount of attenuation is minimized in the vicinity of , so that the near and far impression tube can be further emphasized.

Next, FIG. 3 shows another example of a specific configuration of the audio signal zooming device of the present invention using a 90° phase shift circuit as in 1. here,? The θ phase shift circuit P' is similar to the example shown in FIG.
t, supplied to A12. Variable attenuator A11.112Fi
The inverse motion type variable attenuator has the transmission amplitude characteristics shown in FIGS. 6(A) and 6(B) and Table 1.

Transmission amplitude characteristics of variable attenuators All and A12 When the scales of these variable attenuators As1 and At2 are changed from C to K, the phase difference θ between the input signals of left and right speakers 8Ps and SF3 changes from 0 to The output signals of these variable attenuators Az1 and A12 are supplied to an adder ADD and a subtracter SUB K to obtain the sum and difference outputs of the Ryogawa force signals, and these sum and difference outputs are respectively variable. Speaker βP1 via attenuators A4 and A4 and As and A1
and 8P2 lc respectively. These variable attenuators A4 and AS and A6 and Ayl-i are the third
As in the example shown in the figure, 1. Use a generally used inverse motion type and interlocking type variable attenuator to adjust the left/right direction and overall volume. Mutual correlation coefficient r=.

We will examine the sense of expansion of the temperament in the vicinity of , in comparison with the case where the sound source is a stereo signal.

According to the above-mentioned literature by Kurosumi and Onaka, the correlation coefficient y
It has been shown that the expansion of the sound image is extremely sensitive in the vicinity of +9. Experiments have been conducted on the sound image, and Figure 7 (AIK
It comes to show. Here, the shaded area indicates the spread range of the sound image when the correlation coefficient r=o. In other words, left and right speakers S
The density is high in the vicinity of P1 and SF3, and it is slightly thinner in the center, and has an extremely wide spread range as a whole.

On the other hand, when the correlation coefficient r between the output signals formed based on a single sound source is set to 0, the sound image spread range before and after level correction is shown in Figure 7 (B) and ( In this case, before level correction, the sound image is localized near the speaker of the channel whose phase is leading from the center, and after level correction, As shown in Fig. 7 (CjK?1!l''!), a concentrated sound image is localized in the center.

In other words, by increasing the speaker output of the channel whose phase is delayed by an appropriate amount, the sound image is biased in the direction of Figure 7.
- Figure 7 (The sound image can be returned to the center front as shown in q.0 At that time, the spread of the sound image is left and right. Figure 7 (In the case of IAI, it is much narrower and perceived as seven integrated sound images.The reason for this single-sound image feeling is that in the case of Figure 7 IAI, the sound images in each channel are As for each component within the frequency band, the amplitude and phase of each channel vary completely randomly, so it is not felt as a unified single sound gIK fusion, whereas @Figure 7 (B) In the case of (C1), the amplitude of each Kti component is equal between the left and right channels, and the phase difference between the left and right channels is also constant regardless of the frequency. This is because they are fused together and felt as a single unified temperament.

To summarize what has been said about the above-mentioned document by Kurosumi and Onaka, the conventional sound image localization method according to this document requires l pairs of left and right stereo signals that are completely independent. It cannot be obtained from anything other than special synthesized sounds or noises, and is extremely impractical.If the correlation coefficient r is not zero, that is, if a signal with r=r(lrl~O) is used, the correlation coefficient will be 0. Although it is possible to increase the absolute value of r, it is impossible to reduce it.
Discontinuity occurs at the changing points, and the sense of perspective that changes continuously cannot be obtained.

On the other hand, in the audio signal zooming device according to the present invention described above, the correlation coefficient of the left and right stereo signals formed using the sound source signal of a single child can be continuously changed. 0 that gives you a changing sense of perspective
Versatile perspective control, that is, zooming, could only be realized by the present invention as long as it is based on normal program production methods. As shown in Figure 1, the sound image expands significantly in the vicinity of 0 when moving from far away to near, but audio signal zooming, where the sound image expands once during zooming, can only be used for special purposes in extremely limited cases. This cannot be said to be a general Zuban. In contrast, the spread of the sound image in the audio signal zooming according to the present invention is extremely small, giving the impression of natural zooming.

As mentioned above, the audio signal zooming according to the present invention utilizes the phenomenon that the correlation coefficient of the left and right stereo signals changes and the sense of distance of the sound image changes as a result of the above-mentioned document. This book is by far the best in the world, but in that it can use any monophonic sound source as a sound source, its range of use has been greatly expanded compared to the past, and in the vicinity of the correlation coefficient θ. However, since the width of the sound image hardly expands, it has the great advantage of not damaging the impression of a single sound source, and it has a much greater effect than conventional methods, and can be used in a wide range of applications. It will be done.

Next, K is an audio signal zooming device that is capable of expressing λ-dimensional movement of a sound source in space by combining the audio signal zooming device of the present invention having the above-mentioned functions and effects with a conventional left-right direction control device. The basic operating principle of the is shown in Figures (Al, (Bl).

A knob of an operating section in such a -dimensional zooming device,
When you operate the lever and move the number in the X direction in figure (A),
In the zooming device with the configuration shown in Figure 3, the attenuation amount of the variable attenuators A4 and As changes, and the movement in the positive direction moves the musical temperament to the right, and the movement K in the negative direction causes the sound image to move to the left. move in the direction. In addition, the sense of distance changes in the direction where the distance of the sound image becomes smaller (when moving in the y direction in AI, the distance of the sound image becomes larger than the movement K in the positive direction, and the distance K moves in the negative direction). I will ask you to do so. To this end, the attenuation amounts of the IjI variable attenuators A1 and A2 and A4 and A7 in the configuration example shown in the third figure are changed in conjunction with the movement K in the y direction. That is, specifically #i
, when the position in the y direction is changed from the maximum positive value to the maximum negative value, the attenuation amount of the 1 variable attenuators A1 and A2 is determined by the scale (θ) in the transmission amplitude characteristic of Fig. 6 (B). It changes according to the characteristics when changing from 0 to π, and the variable attenuator A4.
The amount of attenuation of A7 may be changed in a direction that gradually decreases. As a result, for example, if the position of the knob on the operating section is moved according to the locus of one point llA111 in Fig. 1 (Al), the listener will approximately follow the locus of the one point @ line in Fig. You get the impression that the source of the sound is getting closer.

An example of the configuration of the operation section in the one-dimensional zooming device as described above is shown in FIG. 9.
, Vstd, respectively, are pairs of interlocked volume adjusters consisting of variable attenuators A1 and A2, A6 and A7, and A4 and AI in the configuration shown in the third figure, and housed in a shaft, 5LVi, guide 0, which is the slit for
When a knob N, which is located at the intersection of the bars L1 and L2, is moved, for example, in the vertical direction, the bar L2 moves parallel to the earthwork, and the attenuation amounts of the volume adjusters V+ and Vt change in conjunction with each other. Also, if you move the knob N left and right, the par L1 will move in parallel to the left and right, making the sound l1llll rectifier V! The amount of attenuation changes. In addition,
A sweep section with a similar configuration to this can be used to adjust the level of a datayanel audio signal.
This can also be achieved by using a so-called joy stick in which multiple rotary potentiometers are operated in conjunction with a single lever.

In such a case, an interlocking type potentiometer may be used as the potentiometer if necessary.Also, such an operation unit may be realized electronically by a combination K of a CRT display and a light pen. You can also do it.

As is clear from the above description, according to the present invention, the sense of distance of the sound object by the audio signal zooming device is continuously adjusted from the line connecting the left and right speakers to the inner side, that is, to the vicinity of the listener's head. It is possible to obtain an effect of bringing the objects closer together, which was previously impossible, and by using such a zooming effect, it is possible to provide a new program production method for directing and producing stereo dramas and spatial music works. In addition, since such audio signal zooming is based on the use of a monophonic sound register, it is extremely impractical and convenient, and has traditionally been widely used to pan the sound image left and right. Similar to the left-right sound image localization device, the sound image nosooking effect can be achieved using an extremely simple method of use.

In addition, when a general owner adds this audio signal zooming device to a ready-made 10-gram recorder using ordinary radio broadcasts, tapes, discs, etc., the program source must be a single sound source or similar to it. If so, the same zooming effect as described above can be achieved.Furthermore, a conventional zooming device can be used for the sense of distance farther from the line connecting the left and right speakers, and the zoom according to the present invention can be used for the sense of distance closer to the line connecting the left and right speakers. If you use a
It is possible to express the sense of a wide range of distance extremely effectively, and there is no need for any special equipment to use both.

[Brief explanation of drawings]

FIG. 1 shows the basic structure Ff of the audio signal zooming device of the present invention.
A block diagram showing C, Figure 1 is a diagram showing the principle of the property, Figure 3 is a block diagram showing an example of its specific configuration, Figures (A) and (B) ii. A vector diagram and a characteristic diagram showing the operating principle of the variable attenuator in a specific configuration, FIG. 3 is a block diagram showing another example of the specific configuration, and FIG. Similarly, vector diagrams and characteristic curve diagrams showing the operating principles of the variable attenuator in the same equipment, respectively (AI, (B), (C) left and right stereo in the audio signal zooming device) Diagrams each showing an example of the mode of the sound image in the vicinity of the signal correlation coefficient 0, Figure rA11 (Bl is an explanatory diagram of the mode of operation of the one-dimensional audio signal zooming device according to the present invention, Fig. 9 is a plan view showing an example of the configuration of the operating section.S...Monophonic sound source, P...Phase shift circuit, P'.
...9θ phase shift circuit, C...control circuit, SPl, S
P2...Speaker, A1 to A7, A11. A12...variable attenuator, ■
・Polarity inverter, AI) D , , adder, SU
B, , subtractor, Vl, V2, vg-t
yvAes, LI L2...-Lever N...
Knob, SL...Slit for guide. j) 1st Seki @ 2 m θ Ikon 149 E Kenro' @ 3 Figure '7114- Figure' @ 5 Figure i IZ Figure (A) (Roff (C) SPf SP2 Procedural amendment n'l l...3t: I A ll/Mari Toku, ]'F
Agency Director Arrival Kazuo Sugi War 1 Incident Display Samurai Request ff1t Ku7/3g1 No. 2, Name of Invention Audio Signal Zooming Device 3, Interaction with Occluder Case Patent-14+, T, (43
5) As per the attached sheet of the Japan Broadcasting Corporation, 1. Claims S of the specification are corrected as shown in the attached sheet. 2. "Most strictly" on page 7, line 1j of the same is deleted.0 3. The 73rd line of your letter should be corrected to ``signals are mutual.'''f ``signals are mutual.'' 4. Shown in [(A), [Yes]) in the 1st line of the 1st section. all, morning person” as r (AJ, CB) sin, c
Correct to osillJ05, page 1, line 6 [
Change variable attenuation #Ax and A2J to "variable attenuation units 11 and A12"
Correct to J. 6. Correct Figure 3 of the drawings as shown in the attached sheet. Attachment 2, Claims/) Means for drumming a monophonic sound source signal t for one minute; Audio signal zooming characterized by comprising means for continuously changing the value to a desired value to form a drum signal, and means for performing audio signal zooming as the λ branch signal (left and right signals of a stereo sound source). Device. h) In the zooming device according to claim 1, the audio signal is characterized in that the phase difference is maintained at a substantially constant value over almost the entire audible frequency band, regardless of frequency. zooming device. 3) In the zooming device according to claim 1 or 2, the monophonic sound source signal [π/, 2
The branched signals are formed by a phase shift circuit so as to have a phase difference of /coradian from each other, and one of the branched signals is passed through a variable attenuator having a transmission amplitude characteristic of SUa. , the other one is played for another minute, and one of the - branches is -1π/ko≦-≦π when O≦-≦π/-.
The other side of the co-branch is passed through a variable attenuator having a transmission amplitude characteristic of 0 when
01π when ≦-≦/ko 01π/ko ≦-≦-cme
An audio signal zooming device characterized in that the signals are added to each other via variable attenuators having transmission amplitude characteristics. 1) In the zooming device according to claim 1 or 2, the monophonic sound source signal is divided by a π force phase shift circuit for one minute so as to have a phase difference of V coradian, and then the monophonic sound source signal is split into the - branch. A signal rt is formed, and when O≦0≦2, the signals are added and subtracted from each other via variable attenuators having transmission amplitude characteristics of (2)−/ko and sie #/ko, respectively. Audio signal zooming device. j) In the zooming device according to any one of claims 1 to 9, the amplitude of the left and right signals of the stereo sound source is controlled to move the sound image left and right. An audio signal zooming device O characterized by

Claims (1)

[Scope of Claims] 1) Means for splitting a monophonic sound source signal, and an arbitrary desired phase difference between the split monophonic sound source signals from t-0 to π radians over almost the entire audible frequency band. #1 - Means for continuously changing the value to form a one-minute signal; #1 - Means for performing audio signal zooming using the minute signal as left and right signals of a stereo sound source; zooming device. 2. In the zooming device II according to claim 7, the phase difference is applied over almost the entire audio frequency band to KP!, which is independent of frequency. An audio signal zooming rII device that maintains an approximately constant value as a ta image. 3) In the zooming AM according to claim 1 or claim 1, the monophonic sound source signal is split into co-branches using a π/co phase shift circuit so as to have a phase difference of π/coradian from each other to produce the co-branched signal. Of these λ branch signals, one is passed through a variable attenuator with a transmission amplitude characteristic of 100, and the other is further divided into two parts, and one of the two parts is divided into parts such that O≦θ≦π/ When alII#, π/ko≦θ
When passing through a variable attenuator having a transmission amplitude characteristic tube that is 0 when ≦π, the other of the above-mentioned - branches of II, after reversing the polarity, is 0 when 0≦θ≦, and 0 when π/2≦e≦. An audio signal zooming device characterized in that KLI are added to each other via variable attenuators having a transmission amplitude characteristic of -αθ. 4) In the zooming device according to claim 1 or Fi-th λ, the monophonic sound source signal tx/2
The above-mentioned -branch signal is formed by branching to have a phase difference of KE/coradian from each other by a phase shift circuit, and 0≦θ≦
K is added and subtracted from each other via variable attenuators respectively having transmission amplitude characteristics of cm #/J and -θ/ko when π/ko.
? Audio signal zooming device. 5) ``#I!'' in any of paragraphs 7 to 5 of the % forgiveness request. In this zooming device, the amplitude of the left and right signals of the front station stereo sound source is changed to n III @, respectively, so that the sound image is moved left and right.