JP2010119025A - Acoustic playback system and method of calculating acoustic playback filter coefficient - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such the problem that, when measuring head transfer characteristics from a plurality of speakers installed in the rear, in the conventional speaker arrangement, speaker installation positions to be measured also increase accompanied with the increase of rear channels, intervals of speakers installed in the rear become narrow, clear sense of separation is not obtained between virtual sound images created on the basis of resultant head transfer functions, and it becomes difficult to secure sufficient localization precision. <P>SOLUTION: When measuring head transfer functions from a plurality of speakers installed in the rear, the functions are measured by disposing the speakers while considering not only a horizontal plane but also an elevation angle direction and a distance and providing a difference in relative positional relationships between speakers. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sound image localization processing method using a head-related transfer function, and more particularly to a sound image localization processing method having a function of realizing a rear virtual sound image localization using only a front speaker.

  In virtual sound image localization technology, a speaker is installed at a position where a virtual sound image is to be localized in order to generate a virtual sound image, and a head-related transfer function from the speaker to the listener's ear canal entrance (hereinafter referred to as a target characteristic) Need to be measured. Non-Patent Document 1 is widely used as a reference for speaker installation positions when measuring target characteristics. According to this, all the speakers including the rear are placed at a fixed distance in the azimuth determined on the horizontal plane around the listening position of the virtual sound image, that is, the measurement position of the target characteristic. FIG. 2 shows the position of the surround back L speaker 102 according to this ITU-R recommendation. In FIG. 2, the position of the dummy head 103 in which microphones are installed in both ears is also shown. The dummy head 103 may represent the actual head.

  In the figure, the upper figure shows an elevational view, the lower figure shows a horizontal plan view, and the upper and lower figures have the same broken line position connecting the head centers in both figures.

  When actually measuring the target characteristics, in order to generate a rear virtual sound image, a measurement signal is reproduced by installing a speaker at a position where the virtual sound image is to be localized. In FIG. 2, it reproduces | regenerates with the surround back L speaker 102, and measures with the microphone with which the dummy head 103 installed in the measurement position or the both ears of the real head was equipped. Then, a filter coefficient of the head related transfer function for localizing the virtual sound image at the position of the surround back L speaker 102 is calculated, and the sound field is reproduced in the reproduction system using this filter coefficient.

  Here, the number of speaker positions at which the rear target characteristic is measured differs depending on the type of reproduction format. In the case of a 5.1ch system such as a DVD, the surround L and the surround R are two. In the case of a 7.1ch system such as a BD, the surround back L and the surround back R are combined in addition to the two. There are a total of four. Furthermore, since the Super Hi-Vision system, which is one of the next generation surround formats, uses 22.2 channel speakers in the entire sound field, the number of sound sources to be localized rearward is increasing.

In this way, the number of playback channels increases as the surround format becomes the next generation. Accordingly, in the case of the sound image localization processing method that realizes the rear virtual sound image localization using only the front speaker, the number of channels to be reproduced in the rear increases, so that the number of virtual sound images to be localized rearward also increases. Therefore, the rear speaker installation position for measuring the target characteristic by placing the speaker behind in order to generate the rear virtual sound image also increases.
ITU-R BS. 775-1

  By the way, generally, localization based on a virtual sound image tends to have a lower localization accuracy than localization based on a real sound source, and in particular, it is said that the localization accuracy of a rear virtual sound image is worse than that of the front. Since the rear virtual sound images increase, the rear speaker installation positions for measuring these target characteristics also increase, and therefore the rear speaker installation position interval is narrowed.

  For this reason, in the virtual image of the rear where the localization accuracy is originally poor, a sufficient sense of separation between the virtual sound images cannot be obtained, and the virtual sound image that should originally be a separate channel is synthesized and heard as one virtual sound image. Problems such as a reduction in the number of playback channels to be virtually reproduced occur.

  The calculation method of the sound reproduction filter coefficient of the present invention calculates the sound reproduction filter coefficient for localizing and reproducing the sound reproduced from a plurality of speakers arranged so as to be in front of the listening position. Measuring means for measuring the sound reproduced from the speaker, and at least one of the virtual positions is a position that is not on the same horizontal plane with respect to the listening position, and the sound at the position is Including a filter coefficient calculating means for measuring a target characteristic by the measuring means and calculating a filter coefficient based on the target characteristic.

  Further, the two positions that are paired on the left and right sides of the virtual position are either one of the orientation on the median plane, the orientation on the horizontal plane, the distance from the target position to the measurement point, or a combination of two or more The virtual position may be determined so that it is not necessarily symmetrical with respect to the position of the measuring means.

  In the sound reproduction system of the present invention, in the sound reproduction system for localizing sound reproduced from a plurality of speakers arranged to be in front of the listening position at a virtual position, at least one of the virtual positions is: A filter processing unit that performs a filter process on audio signals of sounds reproduced from the plurality of speakers may be provided so as to be localized so as not to be on the same horizontal plane with respect to the listening position. Absent.

  According to the present invention, the audio signal of the sound reproduced from the plurality of speakers is filtered so that at least one virtual position is localized so as not to be on the same horizontal plane with respect to the listening position. Therefore, the feeling of separation of the virtual sound image is improved, and the localization effect of the virtual sound image can be enhanced.

  Also, the two virtual positions that are paired on the left and right sides are not necessarily symmetrical with respect to the measurement position, so that the sense of separation of the virtual sound image is improved and the localization effect of the virtual sound image can be enhanced.

(Embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram comparing the arrangement of surround back L in measurement of target characteristics with a conventional arrangement in the embodiment of the present invention.

  In FIG. 1, the surround L speaker 100 and its installation position, the surround back L speaker 101 and its installation position in the present embodiment, and the dummy head 103 in which microphones are installed in both ears are shown. The dummy head 103 in which the microphones are installed on both ears may be at the actual head position. For comparison, FIG. 1 shows a surround back L speaker 102 and its installation position according to the installation method of the ITU-R recommendation (BS.775-1) as a conventional example.

  FIG. 1 is an elevational view, the lower view is a horizontal plan view, and the upper and lower views are broken lines that connect the centers of the heads in both drawings, and indicate the same position. Here, Em represents an elevation angle when the horizontal plane is a reference on the median plane, Am represents an azimuth angle when the back of the head of the dummy head 103 is a reference (0 degrees) on the horizontal plane, and Dm is a speaker. Indicates the distance from the measurement position.

  Further, in FIG. 1, only the speaker arrangement on the left rear side with respect to the dummy head 103 is shown for the sake of simplicity, but the speaker arrangement also exists on the right rear side.

  A measurement method in the measurement environment configured as described above will be described below. First, measurement with a surround L speaker will be described.

  A measurement signal is reproduced from the surround L speaker 100 and measured by microphones installed on both ears of the dummy head 103. Based on the target characteristics of the obtained surround L speaker 100, a filter coefficient for localizing the virtual sound image at the position of the surround L speaker 100 is calculated.

  Next, measurement with the surround back L speaker 101 will be described.

  The position indicated by the surround back L speaker 101 is not uniquely determined, but is related to the position indicated by the surround L speaker 100. That is, with respect to the target characteristic of the surround L speaker 100 measured at the position of the surround L speaker 100, by changing not only the horizontal plane but also the elevation angle direction and the distance from the speaker to the dummy head or the actual head, A feeling of separation is sufficiently obtained and the localization accuracy is improved as compared with the case where the target characteristic of the surround back L speaker 102 at the position indicated by the L speaker 102 is measured. One method for confirming separation feeling and localization accuracy is, for example, a subjective evaluation experiment.

  A multi-channel surround reproduction system may be configured using the filter coefficients measured as described above. In other words, the virtual positions of the surround speakers and the surround back speakers can be changed in the height direction as compared with the conventional surround speakers and surround back speakers arranged on the same horizontal plane as shown in the ITU-R recommendation. By changing the distance so as to shorten the distance to the actual head, it is possible to configure a surround system that can reproduce surround with a sense of separation and localization.

  In the present embodiment, only the surround back L speaker 101 is moved and the surround L speaker 100 is installed at a general position in the conventional measurement. However, the surround L speaker 100 is also at an elevation angle like the surround back L speaker 101. You may move freely about azimuth and distance.

  Further, in the present embodiment, the measurement position of the target characteristic in the surround R speaker (not shown) is a position that is symmetrical with respect to a straight line on the horizontal plane where the distance from both ears in the horizontal plane view of FIG. 1 is equal. Is not necessarily symmetrical.

  The present invention is useful for a device capable of reproducing a music signal and having two or more speakers, such as a front surround system, a TV, an AV amplifier, a component, a mobile phone, a portable audio device, and the like.

The figure which shows the measurement position for measuring the head related transfer function required for the sound image localization processing system in embodiment of this invention The figure which shows the measurement position of the conventional head related transfer function

Explanation of symbols

100 Surround L Speaker 101 Surround Back L Speaker 102 Surround Back L Speaker 103 Dummy Head

Claims (5)

In a sound reproduction system for localizing sound reproduced from a plurality of speakers arranged to be in front of a listening position at a virtual position,
A filter processing unit that performs filter processing on audio signals of sounds reproduced from the plurality of speakers so that at least one of the virtual positions is positioned so as not to be on the same horizontal plane with respect to the listening position; A sound reproduction system comprising: A method of calculating an acoustic reproduction filter coefficient for localizing and reproducing sound reproduced from a plurality of speakers arranged to be in front of a listening position,
Measuring means for measuring the sound reproduced from the speaker;
At least one of the virtual positions is a position that is not on the same horizontal plane with respect to the listening position, and a sound is reproduced from the speaker at the position, a target characteristic is measured by the measuring means, and the target An acoustic reproduction filter coefficient calculation method comprising: filter coefficient calculation means for calculating a filter coefficient based on characteristics. Two of the virtual positions that are paired on the left and right are either one of the orientation on the median plane, the orientation on the horizontal plane, the distance from the target position to the measurement point, or a combination of two or more, 3. The method for calculating a sound reproduction filter coefficient according to claim 2, wherein the virtual position is determined so as not to be symmetrical with respect to the position of the measuring means. A computer-executable program comprising a step of realizing the calculation method according to claim 2 or 3. A recording medium storing the program according to claim 4.

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