JPH03195199A - Image orienting device - Google Patents

Abstract

PURPOSE:To simplify configuration and to reduce the cost of a device by using a phase shifting circuit with the cascade connection of primary and secondary phase shifting circuit as a main body. CONSTITUTION:The phase shifting circuit is provided with the cascade connection of the primary or secondary phase shifting circuits PS1-PSn, which number is correspondent to the asymmetrical degree of a loudspeaker, so that a phase shifting amount in a low frequency area can be larger than a phase shifting amount in a high frequency area with 1-2kHz as border. A level correcting means EQ is provided so that a level in the high frequency area can be decreased by delayed phase shifting and increased by advanced phase shifting corresponding to the increase of a frequency with 1-2kHz as the border. In such a way, the phase shifting amount is controlled by the primary or secondary phase shifting circuit. Thus, the configuration can be extremely simplified rather than executing a digital signal processing and by providing a frequency characteristic even to the level as well, right and left direction feelings can be increased.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention processes the channel signals of speakers arranged asymmetrically with respect to the listener, so that the channel signals of the speakers are arranged symmetrically with respect to the front of the listener. The appearance is related to a sound image localization device that focuses on the sound source above.

[Conventional technology]

The factors that allow us to recognize the direction of sound and sound image localization are (1) power difference in sound between both ears, (2) difference in propagation time (phase difference) of sound waves between both ears, and (3) incidence of sound in both ears. There are three types: a frequency difference and a phase difference based on the angular difference, of which (1) and (2) greatly contribute to sound image localization.

The listening position of the stereo playback device is now as shown in Figure 10(a).
As shown in , if the left speaker L and the right speaker R are at a point equidistant N1, the factor (1) above, that is, the power of the sound that tends to reach the left speaker and the right speaker R
By adjusting the power of the sound arriving at the two speakers to be equal, a symmetrical sound field in which the sound image moves smoothly between the two speaker powers can be obtained.

In Figures 11 and 12, the center frequency is 500c/s.
, the relationship between the output ratio of the left and right speakers and the localization of the sound source when the sound source is band noise with a width of +Oc/s, and when the band noise with a center frequency of 1.1 kc/s and a width of 22C/S is used as the sound source. This is a copy of the indicated publicly known document.

As is clear from these two figures, the calculated value shown by the solid line and the measured value shown by the * mark almost match, and if the sound power from the left and right speakers is matched, the sound image will be It is proven that it moves smoothly.

By the way, as shown in Figure 10 (old), in-vehicle stereo playback devices have asymmetrical positions of the left and right speakers in front of the listener. However, the distribution of sound between the left and right speakers biases the sound image toward the direction closer to the listener, resulting in an asymmetric sound field.

FIG. 13 is a copy of a known document showing the relationship between sound localization, level difference between left and right speaker channels, and phase value when a sound source having a frequency of 1110C/S is used in an asymmetric sound field. As is clear from this figure, the sound image is biased towards the closer speakers, which supports the whole medicine.

In this case, the distance from the listener to the left speaker L is 1
, when the distance to the right speaker R is 12, if a delay device is inserted in the channel of the right speaker R to delay the distance difference 1 - +, , ) to the listening position by the time converted to the speed of sound, the 10th As shown in Figure (C1), the appearance is equivalent to a sound wave being emitted from the upper position R',
The factor (2) above, that is, the transmission time difference (phase difference) of sound waves between both ears can be made equal.

[Problem to be solved by the invention]

As mentioned above, the inventors of the present application found that if the difference in distance from the left and right speakers is converted to the speed of sound, for example, if the channel signal is delayed by digital signal processing, it is possible to localize a sound image close to a symmetrical sound field. confirmed by.

However, this method requires an A/D converter, a dynamic RAM, a D/A converter, a clock generator, etc. as a system configuration, and has a problem in that the cost of the device is high.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a sound image localization device that can easily realize sound image localization close to a symmetrical sound field with a simple configuration.

[Means to solve the problem]

In general, the left and right speakers in the vehicle and the listening position are the 101st
2+(b) or the relationship shown in FIG. 13 in most cases. When the left and right speakers in the vehicle interior and the listening position have such a relationship, the inventors' experiments have shown that the lower one frequency is, the more the difference in arrival time from the left and right speakers to both ears contributes to central localization. has been confirmed. This phenomenon is described in the document r Journal of the Institute of Electronics, Information and Communication Engineers Vol. 1.72. Nc
i8 Hearing topic "Sound image localization" disclosed by Hiroyuki Miyata et al.
This is also supported by the relationship between the time difference and the sound pressure difference between the signals in which the r sound image is perceived at the center, as shown in FIG. According to this, it can be seen that with a frequency around 1.5 kHz as a boundary, at lower frequencies, the time (phase shift) difference greatly contributes, and at higher frequencies, the sound pressure difference greatly contributes to the sense of left and right direction.

On the other hand, normal stereo music sources are often created with the intention of being listened to in a symmetrical sound field for each instrument, and vocals in particular are often placed in a symmetrical sound field, with the left and right sides at the same level with central localization in mind. In many cases, the frequency band in this case has an upper limit of 1.2 to 2 KHz at most, and when listening to such a source in an asymmetric sound field, the sound image remains biased and the power of the sound from both speakers increases. It was difficult to achieve central localization by simply balancing the

Therefore, the present invention provides a primary phase shift circuit whose number corresponds to the degree of asymmetry of the speaker so that the amount of phase shift in the low frequency range is larger than the amount of phase shift in the high frequency range between 1 and 2 KHz. Alternatively, a phase shift circuit formed by successively connecting a secondary phase shift circuit is provided.

Further, a level correction means is provided such that the level in a high frequency range between 1 and 2 KHz is decreased by a delayed phase shift and increased by an advanced phase shift as the frequency increases.

[For production]

In the present invention, since the phase shift amount is adjusted by a first-order phase shift circuit or a second-order phase shift circuit, the configuration can be significantly simplified compared to when digital signal processing is performed.

In addition, the level in the high frequency range increases as the frequency increases.
By giving a frequency characteristic to the level so that it decreases with a delay phase shift and increases with an advance phase shift, the sense of left and right direction is increased.

〔Example〕

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and particularly shows each signal processing circuit inserted into a channel of a speaker near the listener. In the same figure,
n (n = integer greater than or equal to 2) phase shift circuits ps, ps
,...,ps,ps+2
n-1n and one equalizer circuit EQ are connected in cascade in this order. Among these, the delay time tap s is a first-order phase shift circuit, and the delay time amount is switched by connecting a capacitor C or a capacitor C2 by a switch SW1. Phase shift circuit ps,・
..., ps, ps is 12 n-1
In the nth-order or second-order phase shift circuit, the switch SW2 short-circuits the final stage phase shift circuit PS to reduce the delay amount when the delay amount is too large. Further, the equalizer circuit EQ is used to attenuate the level in a high frequency range, and in some cases, it also sets the power ratio between channels that do not require delay.

Here, as a primary phase shift circuit, for example, as shown in FIG.
The other end is connected to the non-inverting input terminal (◆) of the operational amplifier OP, and a feedback resistor R4 is connected between the inverting input terminal (-) and the output terminal of the operational amplifier oP. It is possible to use a capacitor C connected between the non-inverting input terminal (÷) of oP and the ground point.

In addition, as another first-order phase shift circuit, for example, as shown in FIG. The other end of C is connected to the non-inverting input terminal (◆) of the operational amplifier OP, and a feedback resistor R is connected between the inverting input terminal (-) of the operational amplifier OP and the output terminal.
It is possible to use one in which F is connected and a resistor R is further connected between the non-inverting input terminal (♦) of the operational amplifier OP and the ground point.

Incidentally, when the resistance R of the primary phase shift circuit shown in FIG. 3 is made variable, the relationship between RCω and the phase shift angle is shown in FIG. 4. As is clear from this figure, if RCω;l is set for a signal with a frequency of 200 Hz, the phase shift difference between the input (2) and the output (2) in this case will be 90''.

That is, T(ω)-90°/360°= 1.25m
A time difference Δt1 of 5 ec is obtained.

On the other hand, as a secondary phase shift circuit, as shown in FIG. 5, one end of the series connection circuit of capacitor C1 and resistor R1 is connected to the input terminal, and the other end is connected to the inverting input terminal (-) of operational amplifier OP. At the same time, the other end of the resistor R whose end is connected to the input terminal is connected to the non-inverting input terminal (÷) of the operational amplifier oP, and a feedback circuit is connected between the output terminal and the input terminal of the operational amplifier OP. Similarly, a resistor R2 is connected between the output terminal of the operational amplifier OP and the mutual junction of the capacitor C1 and the resistor R.

Furthermore, it is possible to use an operational amplifier oP in which a resistor Rb is connected between the non-inverting input terminal and the ground point.

Incidentally, when the relationship between the turnout frequency and the phase shift of the secondary phase shift circuit shown in FIG. 5 is expressed using Q as a parameter, it becomes as shown in FIG. 6. Here, Q=1 and 180 at 1 kHz
If the phase shift difference is set to °, T((,1)
-180°/360° = 0.51 sec time difference Δt
2 is obtained.

When the above-mentioned first-order phase shift circuit and second-order phase shift circuit are connected in cascade, Δt1 is added to Δt2, and Δt2 is added to Δt1 with respective frequency differences, resulting in a frequency difference of about 1.0 at 200 Hz.
At 6'm5ec and 1kH2, there is a delay of about 0.94ssec.

FIG. 7 shows the relationship between frequency and delay amount when primary phase shift circuits and secondary phase shift circuits are connected in multiple stages.

In the figure, the solid line indicates the number of connections n, and the dashed line indicates the number n of connections.
is set to 6, and the dashed-dotted line shows the characteristics when the capacitor C7 is switched and connected to c2 using the switch SW1.

As is clear from the characteristic curve in FIG. 7, n=4. n
In any case of =6, the delay plate is large in the so-called band where the time difference is sensitive to 2 to 3 t+++z, and the amount of delay can be gradually reduced at higher frequencies.

Thus, according to this embodiment, a desired delay time can be obtained with an extremely simple configuration, and extremely good sound field localization can be achieved in an asymmetric sound field.

Further, since the phase shift circuit PS1 is configured to switch and connect two capacitors using the switch sW1, it is possible to finely adjust the amount of phase shift.

Furthermore, in this embodiment, an equalizer circuit EQ is provided to attenuate the level in the high frequency range, so it is possible to increase the sense of left and right direction.

In addition, the above fruit 8! An example is a delay circuit that delays the channel signal of a speaker close to the listener, apparently moving the sound source further away.
In other words, a phase-delay signal processing circuit is used, but instead of this, a phase-advancing circuit advances the channel signal of a speaker distant from the listener to bring the sound source closer to the sound source, that is, a phase-advance signal processing circuit is used. It is also possible to use processing circuits.

In addition, in the above embodiment, the phase shift amount was finely adjusted by 2 by connecting the capacitors C and C using the switch SWI, but instead of this, the primary phase shift circuit shown in FIG. It is also possible to adopt a configuration in which the resistor is switched and connected to the resistor, and furthermore, the adjustment is not limited to the primary phase shift circuit, but may be made to adjust the secondary phase shift circuit.

Please note that this fine adjustment may vary depending on the car model, such as the sound field inside the car.
This is extremely effective when there are differences in the position of the driver relative to the speaker, but for example, it is possible to connect a primary phase shift circuit in multiple stages and use a variable resistor or voltage variable resistance element in each stage to continuously vary the phase shift circuit. It is also possible.

Furthermore, if an inductance L is used in place of the capacitor C of the primary phase shift circuit in the above embodiment, it will work to relatively reduce the amount of delay.A similar function is shown in FIG. As shown in the figure, it can also be realized by a variable delay time circuit suitable for a bulk circuit consisting of a gyrator configuration and a variable impedance circuit.

The load circuit including the second operational amplifier viewed from the non-inverting input terminal (♦) of the phase-shifting operational amplifier OP in FIG. 8 is equivalent to the inductance L, and the inductance L1.
It can be replaced with L2.

In addition, impedance Z1. If Z2 includes a voltage or current variable element and this is controlled externally, RL ω
, R2L2ω changes, and as a result, the delay time can be changed continuously.

〔Effect of the invention〕

Although the apparent correction of the sound source position in an asymmetric sound field is possible by employing digital signal processing, it has not been realized because it involves an increase in circuit scale. Note that B B D (Bucket
Brigade Device) could be applied, but the operating upper limit of the clock frequency is low, and S/
This tends to cause deterioration of the N ratio and is not used in practical use.

Since the present invention uses a phase circuit mainly consisting of a cascade connection of a primary transfer circuit and a secondary phase shift circuit, the configuration can be significantly simplified and the cost of the device can be significantly reduced.

In addition, by adding a level correction circuit in which the level in the high frequency range decreases with a delayed phase shift and increases with an advanced phase shift as the frequency fi number increases, it is possible to give a sense of direction by sound pressure difference. is made of.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a signal processing circuit according to an embodiment of the sound image localization device of the present invention, and FIGS. 2, 3, and 5 show detailed configurations of the main elements of the embodiment. circuit diagram,
4, 6, and 7 are diagrams showing the relationship between frequency and phase shift, respectively, to explain the operation of the same embodiment;
FIG. 8 is a block diagram showing another embodiment of the present invention, and FIG. 9 is a block diagram showing the sound pressure level difference and W
Diagram showing the relationship between the t difference and the frequency as a parameter, Figure 10 (al~(C1 is a theory showing the relationship between sound image localization in a symmetric sound field and an asymmetric sound field.
12 and 13 are diagrams showing the relationship between the speaker output level and the direction of the sound source in a symmetric sound field and an asymmetric sound field. PS...Primary phase shift circuit, PS2~PS...
- Primary phase shift circuit or secondary phase shift circuit, EQ...equalizer circuit, sw, sw2...switch. Figure 4 Figure 7 Figure Figure 8 Figure 8 (O) Figure 0 (C)

Claims (2)

[Claims] (1) In a sound image localization device that processes channel signals of two speakers arranged asymmetrically with respect to a listener and creates an apparent sound source in a direction symmetrical with respect to the front of the listener, the speaker The channel signal of one speaker closer to the listener is delayed by a time difference depending on the degree of asymmetry of A sound image characterized by comprising a phase shift circuit in which a first-order phase shift circuit or a second-order phase shift circuit is connected in series so that the amount of phase shift in a frequency range is larger than the amount of phase shift in a high frequency range. Stereotaxic device. (2) It is characterized by being equipped with a level correction circuit such that the level in a high frequency range between 1 and 2 kHz decreases with a delay phase shift and increases with an advance phase shift as the frequency increases. The sound image localization device according to claim 1.