JPS5918920B2 - Onkyo Shingo Saisei Souchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an audio signal reproducing device, and particularly to an audio signal reproducing device that improves sound image localization.

In conventional two-channel stereo, recording is performed using a single-point microphone or multiple microphones to obtain two-channel left and right stereo signals, and these left and right stereo signals are fed to speakers placed in front of the listener on the left and right. .

In such conventional two-channel stereo, a sense of presence is created by the level difference between the left and right stereo signals, but the reproduction of the sense of distance between the front and rear is insufficient, and it is not possible to localize outside the left and right speakers.

In the present invention, we consider that the direction and distance of a sound source are recognized only by the complex sound pressure ratio between the left and right ears, and two speakers, etc. This system clarifies the localization of the sound image by making it possible to perceive the sense of distance by generating the sound using an acoustic transducer.

Further, the present invention aims to provide a circuit with good characteristics and a simple configuration for forming two signals having a desired complex sound pressure ratio.

First, to describe the basic idea of the present invention, when a single sound source S exists at a distance R at an angle θ clockwise from the front of the face as shown in FIG. The transfer functions for the inlet are DL(R2O) and D, respectively.
Letting R(R2O), the ratio between the two DR(R2O) DL (R1°e) °°""°(1) corresponds to the interaural complex sound pressure ratio.

On the other hand, as shown in Fig. 2, the left and right speakers SPL and S
When PR is excited with the values AL and AR (both are complex numbers), the interaural complex sound pressure ratio is AR-DR (
γ, θ) 10AL −DB(γ, −〇) γT=□ AL @DL(γ, −θ) 10AR−DL (γ, θ)・
・・・・・・・・・(2) It becomes.

However, rl θ is the distance and angle to the speaker, and it is assumed that the speaker is arranged symmetrically with respect to the head.

If equations (1) and (2) match, the following equation holds true.

That is, by replacing AR/AL with α, the above equation (3) can be changed as follows.

DL(R2O)・α・DR(r,θ) 10DL(R2O
)・DR(r,-θ)-DR(R2O)・DL(r,-
〇)+DR(R, θ) ・αDL(r, θ
＞

,,,hit,a4)
Therefore, α(DL(R2O)°DR(r,θ)−DR(R2O)
・DL(r, θ))-DR(R2O)・DL(r,-〇)--Dt, (R2O)・DR(rl-θ)
...-
---...(5).

The reason why Equations (1) and (2) match is that the conditions for the sound image from the speaker to reach the point (R2O) are DR(R2O), DL(r, -θ) -Dt, (Rl
e) -I)R(r, -a) -・-・-
(5) DL (R2O)・DR(r1θ) −DR((
This is a case where the speaker is excited so that R2O)-DL(r, θ).

From the above equation (3), (r=2./'Tm, θ=45°
), when the speakers SPL and SPR are placed at the positions of
In order to focus the sound image on the point (R, θ), the conditions for exciting each J speaker, that is, level 1 ALl and IA
When the characteristics of R+ and phase difference (ArgAR/AL) are determined by theoretical calculation, the characteristics are shown in FIGS. 3 to 6.

Figure 3 is for (θ-15°), Figure 4 is for (θ-30°), Figure 5 is for (θ-600), and Figure 6 is for (θ = 90°). , the distance R to the sound image is 0.5 (
m), 1.0 (m), 2.0 (m, l, 2J7 [m],
4.0 (m), the values when changed to ■ are plotted.

The following is recognized from these FIGS. 3 to 6.

First, when the sound image is at approximately the same distance as the speaker or longer, the phase difference is always around 0° at low frequencies (500 kHz, l or less), which means that it remains constant even if the localization angle changes, so Localization is possible using only the level difference between the left and right speaker outputs, but a phase difference is required when high frequencies are included or when the distance between the sound images is small.

Differences in speaker excitation conditions depending on the distance of the second sound image mainly appear in the phase difference of low frequencies when the distance of the sound image is short.

In other words, in Figures 4 to 6, the phase difference and level difference at low frequencies both change even if the distance is small, so it is necessary to take both of these into account when localizing the sound image. In this case, there is almost no change in the level difference at low frequencies, but there is a large change in the phase difference, so in this case, it is possible to localize the sound image using only the phase difference.

Thirdly, if we move the speaker a distance in the same direction and compare the excitation conditions, the excitation conditions will hardly change.

In other words, the localization of the sound image does not depend on the position of the speaker.

Fourth, level differences tend to decrease with frequency.

However, above ICkHz), the characteristic becomes wavy.

Hereinafter, with reference to FIG. 7, the speakers SPL and S
2 supplied to these speakers so that the PR can be excited.
An embodiment of the present invention will be described in which two signals AL and AR are formed.

In FIG. 7, 1 indicates an input terminal, and 2R and 2L are output terminals from which signals AL and AR are generated, respectively, to be supplied to the left and right speakers.

The input signal is passed through a buffer 3 to a means for producing different frequency characteristics between the two signals, such as a high-frequency attenuation filter 4.
and is supplied to the low-pass attenuation filter 5.

The output signal of the high-pass attenuation filter 4 is supplied to an adder circuit 7 via an inverter 6, and the output signal of the low-pass attenuation filter 5 is supplied to a delay circuit 9 via an inverter 8.

The delay circuit 9 is configured as an analog delay circuit including, for example, a plurality of charge transfer elements, and its delay time Td is determined by the number of elements and the frequency of the clock pulse generated by the clock pulse generator 10.

The output signal of this delay circuit 9 is supplied to a subtraction circuit 12 via an amplifier 11 with input and output in phase.

Further, the output signal of the amplifier 11 is supplied to the adder circuit 7 via the variable attenuator 13, while the output signal of the above-mentioned high-frequency attenuation filter 4, which is passed through the inverter 6, is supplied to the variable attenuator 1.
4 to the subtraction circuit 12.

Then, the output of the adder circuit 7 is guided to the output terminal 2R via the buffer 15 and the correction phase shifter 16, and the subtracter circuit 12
The output of is led to the output terminal 2L via the buffer 1T.

Amplifiers 19R and 1 are connected to these output terminals 2R and 2L, respectively.
Speakers SPR and SPL are connected via 9L.

In FIG. 8, the characteristics of the high-frequency attenuation filter 4 in the embodiment of the present invention described above are shown by a broken line 21, the characteristics of the low-frequency attenuation filter 5 are shown by a broken line 22, and the delay by the delay circuit 9 is shown. When the time Td is 500 [μS], the respective levels 1AR1 and IALl of the signals AR and AL generated at the output terminals 2R and 2L and the phase difference A rg (AR/AI, ) between the two are shown by the solid lines in FIG. It will be shown as follows.

Considering level 1 AR1 and IALl, 500
Below 1000 Hz, the level difference between the two signals is determined mostly by the characteristics of the high-frequency attenuation filter 4 and the low-frequency attenuation filter 5.

Since the delay time Td is 500 [μS], (2
, 4, 6......) (kHz), the input and output signals of the delay circuit 90 are in phase, and (1, 3, 5......) )(kHz
) Regarding the signal component of the frequency ('!, delay circuit 9
The input and output signals of are in opposite phase.

Since the phase difference caused by the high-frequency attenuation filter 4 and the low-frequency attenuation filter 5 can be ignored in the high frequency region, the signals appearing at these outputs are considered to be substantially in phase.

Therefore, since the output of the inverter 6 is subtracted from the signal obtained by the output of the delay circuit 9 being amplified by the amplifier 11, the output of the subtraction circuit 12, that is, the level 1ALl is (2, 4, 6...
It becomes a small level at the frequency of (・・・・・・) CkHz), and it becomes a small level at the frequency of (1, 3, ...) CkHz).
It is possible to realize a wave-like frequency characteristic that reaches a large level at the frequency of .

On the other hand, the frequency characteristic of the output I ARl of the adder circuit 7 is conversely high at a frequency of (2, 4, 6...) (kHz), and (1, 3, 5...・・・・・・
It will be clear from the above explanation that the level is small at a frequency of ) (kHz).

Next, regarding the phase difference Arg (AR/AL) between the two, this mainly occurs in the delay circuit 9.

If the delay time Td is 500 [μS], 0.5 (k
- for a signal of 1 (kHz), π for a signal of 1 (kHz),
For a 2 (kHz) signal, 2π, 3CkHz,
The phase difference becomes more dog-like as the frequency increases, such as 3π in the case of a signal of l, resulting in the characteristics shown in FIG.

This characteristic peaks at ±180° due to the characteristics of the measuring instrument, but for example, 2 (kHz
) shows that it is 2π.

In addition, in the low frequency region below 0.5 (kHz), the phase characteristics of the high-frequency attenuation filters 4 and 50 are affected, and along with this, the correction by the correction phase shifter 16 works at low frequencies, so that only the delay circuit 9 The phase difference is made smaller than in the case where

If the resistor connected to the collector of the transistor 18 is R and the capacitor connected to the emitter is C, the correction phase shifter 16 has a phase delay of 2πCR − at the cutoff frequency (f −−). However, in the high frequency region, there is a constant (π) phase delay.

Through the above operation, the two signals generated at the output terminals 2R and 2L have level characteristics and phase characteristics shown by solid lines in FIG. 8.

These signals are then input to amplifiers 19R and 19L, respectively.
The signal is supplied to the left and right speakers SPL and SPR via the .

In other words, the excitation conditions for the left and right speakers SPL and SPR are nothing but those shown in FIG.

Here, the characteristics shown in FIG. 4 and FIG. 8 drawn by the above-mentioned theoretical calculation coincide with each other.

In other words, according to one embodiment of the present invention, θ
For example, the sound image can be localized at a position of R=2 m at −30°.

In addition, when R is other than 2 m, the level characteristics do not change much and can be approximated by adjusting the variable attenuators 13 and 14, and the phase characteristics differ depending on the distance of the sound image in the low frequency region. It is possible to make the phase difference different from that shown in FIG. 8 by inserting a phase shifter similar to the correction phase shifter 16 after the buffer 7 and selecting the cutoff frequencies of both.

Furthermore, when θ is other than 30°, the frequency interval between the wavy peak and dip of the level characteristic is not 2 (kHz), but in this case, the delay time Td of the delay circuit 9 is set to 50°.
It may be set to a value other than 0 [μS].

In short, according to the present invention, all the characteristics shown in FIGS. 3 to 6 can be realized.

Of course, the characteristics shown in FIGS. 3 to 6 are that the speaker
In the case where it is placed at the position of θ-45°),
Even when the speakers are placed in other positions,
The trends are similar, and the present invention can be applied to such cases as well.

Further, as shown in FIG. 9, circuit networks for forming two signals to be supplied from the single sound source to the left and right speakers are, for example, 30a, 30b, and 30c.

A signal from a sound source located at a distance R and an angle θ is provided to each input terminal 1a to 1d, and the output terminal of each circuit network 30a to 30d is connected to a right channel and a left channel. If the configuration is such that the signals obtained at this common connection point are supplied to the speakers SPR and SPI via amplifiers 19R and 19L, respectively, it can be applied to a plurality of sound sources.

Furthermore, as shown in FIG. 10A, a high-frequency attenuation filter 4
and a low-pass attenuation filter 5 into an addition circuit 7 and a subtraction circuit 12
It may also be inserted into the output side of, as shown in Figure 10B,
It may also be inserted between the delay circuit 9, the addition circuit 7, and the subtraction circuit 12.

However, in FIG. 10, the buffers 3, 15.17, inverter 6.8, amplifier 11, and correction phase shifter 16 are not essential components and are therefore omitted.

As is clear from the above, according to the present invention, the sounds from the speakers SPL and SPR have the same transfer function as when there is a single sound source at a predetermined position, so sound image localization is important. It can be clearly positioned, and it can also be localized in a range outside the left and right speakers, and a sense of distance can be achieved in a small distance range.

In addition, as a device for realizing the level characteristics and phase characteristics shown in Figs. 3 to 6, an input signal is first divided into a plurality of frequency components using a band-pass filter, and each of the divided components has a predetermined characteristic. One idea is to apply it to the left and right channels that have level adjustment means and phase shift means, and then mix the left and right signals formed from each component, but this would result in an extremely complicated configuration and difficult to approximate characteristics. be.

On the other hand, according to the present invention, the desired phase characteristics are realized by the delay circuit 9, and the level characteristics mainly at high frequencies are realized by using the mixing means, so the configuration is simple and the characteristics can be approximated very well.

Furthermore, the pinaural system is known as a system that can achieve good sound image localization, but the pinaural system requires recording with a dummy head microphone, and also has the disadvantage that playback must be performed using headphones.

In the present invention, left and right signals can be formed from each sound source collected by a microphone or from the playback output of a master tape, and the speakers can be excited using these signals, so a dummy head microphone is unnecessary and playback using headphones is possible. The benefits are not limited to.

Of course, the present invention can also be applied to playback using headphones.

However, in this case, the required characteristics are different from those for speaker excitation shown in Figures 3 to 6, and it is necessary to directly realize the transfer function of sound reaching the left and right ears from the sound source S at the position (R2O). is necessary.

Figures 11 and 12 show (R=2./T silkworm, θ=45
When a sound source is located at a position of 1°), the characteristics and phase difference (A
There is also a note showing rg(DR/DL)).

The level and phase characteristics shown in FIGS. 11 and 12 can also be realized by the present invention by selecting the frequency characteristics of the filter.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing the position of the sound image and the arrangement of the speakers, Figures 3 to 6 are diagrams showing the theoretical values of the excitation conditions of the left and right speakers for localizing the sound image at a predetermined position, FIG. 7 is a system diagram of one embodiment of the present invention, FIG. 8 is a diagram showing its characteristics, FIGS. 9 and 10 are system diagrams of other embodiments of the present invention, and FIGS. 11 and 12. is a diagram showing the transfer function of sound reaching the left and right ears from a single sound source. S is a sound source, spL and spR are speakers, 1 is an input terminal, 2R, 2L are output terminals, 4 is a high-frequency attenuation filter, 5 is a low-frequency attenuation filter, 7 is an addition circuit, 12 is a subtraction circuit, 9
is a delay circuit.

Claims (1)

[Claims] Between the 11 input terminals and the two output terminals, one input signal supplied to the input terminal is sent to the first and second output terminals, the level ratio and phase difference of which change depending on the frequency.
A circuit network is provided to convert the signal into an output signal, and this circuit network converts one signal led to the above two output terminals to the other signal, which has a small phase difference in the low band and a large phase difference in the high band. means for relatively delaying one signal with respect to the other signal such that the two relatively delayed signals are added and subtracted to obtain two different signals; A high-frequency attenuation filter is inserted into one signal path before or after addition/subtraction, and a low-frequency attenuation filter is inserted into the other signal path, and these filters and the means for performing the addition/subtraction are used to reduce the low frequency band of the input signal. has a large level difference between the above two signals,
In a high band, the level difference between the first and second signals is controlled so that the level difference between the two signals becomes small.
An acoustic signal reproducing device characterized in that the signals are supplied to respective acoustic transducers.