JPH0546160B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for adding elevation localization information of a sound source to a two-channel stereo signal.

In recent years, technological development has made remarkable progress, and the current stereo reproduction system has been widely put into practical use by arranging two speakers in a horizontal plane and localizing the sound image within the distance between the speakers. However, controlling sound image localization in the vertical direction is generally difficult and has not yet been realized.

This is a diagram showing an acoustic transmission system from the sound source 1 arranged on the three-dimensional sphere shown in FIG. 1 to the eardrum of the audience member 2, and FIG. 2 shows its equivalent circuit. In the figure,
H _M is the acoustic transfer function of the entire system, H _S is the spatial acoustic transfer function from the sound source to the listener's head, _HD is the listener's head acoustic transfer function, and H _P is the psychoacoustic transfer function.
Listener 2's sense of sound image localization is obtained from equation (1).

H _M = H _S・H _D・H _P ...(1) Here, generally, H _S and H _P are the sound sources (γ...θ)
is considered to be constant even if θ is different, so H _M
is considered to be the same as the head acoustic transfer function _HD .

Figures 3a to 3f are diagrams showing the actually measured acoustic transmission frequency characteristics of the ear for sound in the elevation angle direction in the median plane (characteristics normalized by the characteristics for the frontal direction, expressed in 1/3 octave bands), and as the elevation angle increases. It also shows that it increases especially in the high frequency band of 5 to 9 KHz.

This invention aims to realize sound image localization in the elevation direction by utilizing the above phenomenon, and in two-channel stereo reproduction, the right (R) channel speaker,
In addition to horizontal localization control by the left (L) channel speaker, localization information in the elevation direction is added.

Two channel stereo systems that are currently widely used include the binaural system shown in FIG. 4 and the stereo system shown in FIG. In the former, the sound being played generated by the sound source 1 is picked up by the microphones 5 and 6 attached to the binaural (R) and (L) channels of the dummy head 4, and the output is sent to the R amplifier 7 and the L channel. This is a system in which the signal is amplified by an amplifier 8 and listened to by the listener 2 using R and L receivers 9 and 10. In addition, in the latter two-channel stereo system, the sound generated in Sound 1 is transmitted to R
microphone 5 for L, microphone 6 for L,
The respective outputs pass through the R amplifier 7 and the L amplifier 8, and then the R speaker 11 and the L speaker 12.
In this method, stereo sound is played back and listened to by listener 2.

FIG. 6 is a block diagram of one embodiment of the present invention. The high frequency characteristics of the stereo amplifier of the normal stereo playback device shown in Fig. 4 or Fig. 5 are controlled by a separately provided elevation direction localization information signal of the incoming sound source, and the tone is changed to give a sense of up and down. This is what I did.

First, in order to obtain an elevational localization information signal of the sound source 1, a pair of directional microphones 13 and 14 are placed vertically at a certain distance to collect sound in the central area of the sound field. Microphone 1
As shown in FIG. 7, the elevation angle directional characteristics No. 3 and 14 are designed to obtain a reference output for the horizontal direction of arrival and to rise as the elevation angle increases. The outputs of the microphones 13 and 14 are amplified by amplifiers 15 and 16, respectively, and then the output ratio is determined by a comparator 17, and this comparison signal is detected by a wave detector to obtain an elevation direction localization information signal.

On the other hand, the output of the R microphone 4 and the L microphone 5 for normal stereo listening, which are placed at a certain distance horizontally in another sound field, is used for R,
After being amplified by the L amplifiers 19 and 20, the delay time τ passes through the elevation direction localization information detection circuit system.
After passing through delay circuits 21 and 22 for compensating the
The R channel and L channel signals are frequency-divided through the R channel and L channel signals, respectively. It is desirable that the crossover frequency at this time is divided by approximately 4KHz.
27 and 28 are delay time compensation circuits inserted after the high frequency converters 25 and 26 to compensate for the delay time difference between the low frequency converters 23 and 24. 2
9 and 30 are amplifiers for increasing the level of the high frequency band signal whose amplification factor is controlled by the elevation direction localization signal; 31 and 32 are for the R channel by again synthesizing the low and high frequency components of each channel; A synthesis circuit 33 and 34 are amplifiers that create a signal with an elevation localization signal added for the L channel, and speakers 11 and 12 for the R and L channels provide the listener with a sense of localization in the left and right directions of the sound source. At the same time, it outputs sound to which is added an elevation direction localization signal that supports the sense of localization in the elevation direction.

In the above embodiment, a configuration was shown in which a high frequency band signal whose level was adjusted based on the elevation direction localization information signal is added to both the left and right channel signals. The gain control amplifiers of both right channels may be controlled to control the gain in the high frequency band to increase the level of the high frequency component.

This invention adds acoustic elevation localization information to a stereo signal in which the level of the 5 to 9 KHz frequency band of both left and right channels of the stereo signal increases as the elevation angle position of the sound source increases. , it is possible to give the listener a sense of elevational localization of the sound source.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the state in which a sense of localization of a sound image is formed, Figure 2 is its composition diagram, and Figure 3 shows how the acoustic transmission frequency characteristics of the ear change with respect to the elevation angle for a sound source in the elevation angle in the median plane. 4 is a block diagram of a binaural system, FIG. 5 is a block diagram of a stereo system, FIG. 6 is a block diagram of an embodiment of this invention, and FIG. 7 is a microphone used in this embodiment. FIG. In the figure, 1 is a sound source, 2 is a listener, 4 is a dummy head, 5 and 6 are R and L microphones, 7,
8, 15, 16, 19, 20, 33, 34 are amplifiers, 9, 10 are R and L receivers, 11, 12 are R and L speakers, 13, 14 are upper and lower speakers, 17 is a comparison circuit, 18 is a detection circuit, 21,
22 is a delay circuit, 23 and 24 are low frequency devices, 2
5 and 26 are high frequency amplifiers, 27 and 28 are delay compensation circuits, 29 and 30 are amplifiers, and 31 and 32 are synthesis circuits. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. Each output signal obtained by a set of microphones arranged vertically at a predetermined interval and having a directional characteristic in which the output increases as the elevation angle of the sound source increases. The high frequency band signal level of a multi-channel stereo signal obtained by collecting acoustic information from the sound source using a plurality of microphones is increased as the elevation angle of the sound source increases according to the difference signal. A method of adding elevation angle localization information of a sound source to a stereo signal. 2 Stereo signal detection means for collecting acoustic information from a sound source using a plurality of microphones and detecting stereo signals of a plurality of channels; elevation angle detection means for detecting the elevation angle of the sound source by a comparator that outputs a difference signal between the outputs of a pair of microphones arranged at intervals of . A device for adding sound source elevation angle localization information to a stereo signal, comprising: a correction means for increasing the signal level of a high frequency band of the stereo signal of the plurality of channels as the elevation angle of the sound source increases according to the output signal.