JP2007081710A - Signal processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a signal processing apparatus and a sound image localizing apparatus for using only outputs of speakers existing in front of a listener so as to surely provide sound image localization as if to be "heard right behind". <P>SOLUTION: The signal processing apparatus includes: a rear localization adding section 131 for adding rear localization by using a head transfer function from the rear side to both the ears of the listener in order to mixing a 6-channel (ch) sound source down into 2 channels; and a crosstalk cancel correction circuit for making the effect of the addition of the rear localization effective. The rear localization adding section 131 furthermore includes a filter 131S for receiving a rear sound signal input SBC to apply signal processing thereto, uses a head transfer function for providing virtual localization from in a diagonally backward direction and employs gain adjustment filters G1, G2 and delay amount adjustment filters D1, D2 to draw the sound localization in the right rear direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sound image localization apparatus including a filter that outputs and adds virtual localization in the back from two real speakers in front.

  2. Description of the Related Art Conventionally, an acoustic system that provides a surround effect by placing three speakers in the front and two to four speakers in the rear so as to surround the listener has been put into practical use. Such a surround effect particularly provides a sound image localization of an object moving in the front-rear direction together with an image displayed on the display screen, and realizes an environmental sound field of a scene displayed on the display screen in the entire viewing space. Used for.

On the other hand, since such a large-scale speaker system is not always practical, only the front speaker is used, and the sound that simulates the transfer characteristic from the virtual rear speaker to the viewer is output from the front speaker. By doing so, there has been proposed a virtual surround system that forms a sound field as if a speaker exists behind (see, for example, Patent Document 1).
Patent Document 1 discloses a stereo sound device that performs crosstalk cancellation and sound field formation using a result of measuring a head-related transfer function measured using a dummy head in advance.
JP 2001-086599 A

  As described above, the virtual surround system's front / rear determination uses the fact that the frequency characteristics differ depending on the positional relationship from the sound source (speaker) to the listener. Even if there is a sound source directly behind, the difference is such that the listener misunderstands that he is pronounced in front. This is because the frequency characteristics of the auditory characteristics entering the human ear are almost the same except for a difference of only a few dB when compared in the front-rear direction. This is because they are localized. Therefore, it has been difficult to localize a sound image so that it can be “sounded from behind”, even with the use of an actual speaker as described above. As described above, it is not an ideal arrangement to arrange “sound from right behind” by arranging two speakers diagonally in the rear direction and one speaker in the back direction. Therefore, if the sound image is localized at the position of the actual speaker, A 7-channel system in which real speakers are arranged on the left and right sides of the most backward direction that can be felt, has been put into practical use, and can be heard from the very back. In this way, it is difficult to create a sound field that can be “sounded from behind”, even with real speakers. Even if a sound image localization device is used, most listeners feel that they can hear from the front, but the surround effect is also dragged so that the localization in the back direction is localized forward, and the overall surround effect is achieved. There was a problem of adverse effects.

  In view of the above-described problems, an object of the present invention is to provide a signal processing device and a sound image localization device that can provide sound image localization that can be reliably “sound from right behind” using only the front speaker output.

In the present invention, means for solving the above-described problems are configured as follows.

(1) The present invention
A signal processing device including a rear localization addition filter that adds a rear virtual sound image localization to an audio signal output from outputs of two front real speakers,
The rear localization additional filter is:
A direct path simulation filter comprising a filter simulating a propagation path in a direct direction from a preset oblique rear position to a listener's ear near the position;
Cross path simulation filter consisting of a filter simulating the propagation path in the cross direction from the oblique rear position to the ear of the listener far from the position;
And a gain adjustment unit that is connected in series to at least one of these path simulation filters and has a filter characteristic set so that the gain levels of the pair of simulation filters approach each other.

When the human auditory sense recognizes the left-right direction, it senses mainly by the phase difference based on the volume ratio of the sound heard by the left and right ears and the difference in reach, and when it recognizes the front-rear direction, it senses by the frequency characteristics. ing.
Therefore, according to the present invention, the sound from the rear direction is obtained by processing the sound source for the rear by the direct path simulation filter that simulates the propagation path from the diagonally backward direction and the cross path simulation filter. Can be easily recognized. However, since this alone does not wipe away the sensation heard from behind the “oblique”, the present invention uses the pair of gain adjustment units in series with each of these filters to convert the pair of gains to the direct path simulation filter and the cross path simulation. Since the filter gain level is set closer, using a model head-related transfer function that simulates the propagation characteristics of the sound from the diagonally backward direction to the ear, the sound is input as if the sound source is attracted to the rear. The signal can be adjusted. Unlike the case where the rear localization is simply reproduced using the head-related transfer function that reproduces the spatial propagation from the back sound source to both ears, the frequency characteristics that contribute to the formation of a sense of localization in the horizontal direction of the human and the front and rear By effectively utilizing the gain ratio that contributes to the formation of a sense of orientation in the direction, it is possible to perform signal processing that provides sound image localization that can be reliably “sounded from behind”.

  As described above, the present invention does not simply use the head-related transfer function but also simply uses the gain ratio. If the head-related transfer function is simply used, it is quite difficult to “sound from behind” as described above. Even if the localization feeling in the front-rear direction is simply adjusted using the gain ratio of the front speaker output, there is a great difference from “being heard from behind”.

  The head-related transfer function is already known from all directions measured at a predetermined angular step size. To adjust the localization in the left-right direction when using the head-related transfer function, the head-related transfer function itself can be used. It can be considered that an accurate propagation characteristic can be obtained in accordance with the above-described measurement data by exchanging the one for the angle. Therefore, it is common to apply the head-related transfer function as such. However, as described above, it is quite difficult to “sound from behind” by simply using the head-related transfer function. In the present invention, the gain between the “pair of frequency characteristics” simulating the propagation characteristics entering the both ears from the virtual sound source is simply using the gain ratio or simply using the frequency characteristics. It is decisively different from being. In the present invention, the volume ratio that greatly contributes to the formation of the left and right localization feeling and the frequency characteristics that greatly contribute to the formation of the front and rear localization feeling are skillfully combined, so that it is possible to realize a localization feeling that can be heard from behind.

(2) The present invention
A signal processing device including a rear localization addition filter that adds a rear virtual sound image localization to an audio signal output from outputs of two front real speakers,
The rear localization additional filter is:
A direct path simulation filter comprising a filter simulating a propagation path in a direct direction from a preset oblique rear position to a listener's ear near the position;
Cross path simulation filter consisting of a filter simulating the propagation path in the cross direction from the oblique rear position to the ear of the listener far from the position;
A delay adjustment connected in series to at least one of the pair of simulated filters and having a filter characteristic so that a delay difference based on a difference in arrival time between the direct path and the cross path included in the pair of simulated filters approaches Part.

  The present invention is the same as the configuration of (1). However, unlike the configuration of (1), the present invention uses a phase difference that contributes to the formation of a sense of orientation in the horizontal direction. That is, the delay adjustment unit causes the delay amount based on the arrival time difference between the direct path and the cross path to be included in the direct path simulation filter and the cross path simulation filter so that the pair of delay amounts approach each other. Since it is set, the same effect as (1) can be obtained by this means.

(3) The present invention
A signal processing device including a rear localization addition filter that adds a rear virtual sound image localization to an audio signal output from outputs of two front real speakers,
The rear localization additional filter is:
A direct path simulation filter comprising a filter simulating a propagation path in a direct direction from a preset oblique rear position to a listener's ear near the position;
Cross path simulation filter consisting of a filter simulating the propagation path in the cross direction from the oblique rear position to the ear of the listener far from the position;
A gain adjusting unit that is connected in series to at least one of these path simulation filters, and in which a filter characteristic is set so that the gain levels of the pair of simulation filters approach each other;
A delay adjustment connected in series to at least one of the pair of simulated filters and having a filter characteristic so that a delay difference based on a difference in arrival time between the direct path and the cross path included in the pair of simulated filters approaches Part.

  If comprised in this way, since the said direct path | route simulation filter, the said cross path | route simulation filter, the said gain adjustment part, and the delay adjustment part are provided, there can exist an effect similar to the above-mentioned (1) (2). .

(4) The present invention
The audio input signal to be input is a 2ch audio signal set for left and right diagonally backward directions,
The rear localization additional filter is provided for each of these audio input signals.

  If comprised in this way, the signal processing which exhibits the said localization effect will be attained with respect to the audio signal of 2ch set for right and left diagonally backward directions.

(5) The present invention
It has an input for inputting multi-channel audio signals,
The rear localization addition filter divides an input signal for surround back center into 2ch as an audio input signal for the rear speaker, and includes the rear localization addition filter for each.

  If comprised in this way, there can exist the effect of said invention using only the source of the input signal 1ch for surround back centers.

  According to the present invention, “both” of the frequency characteristic that influences the sense of front and back of a human and the volume difference or phase difference that influences the sense of right and left is skillfully combined, so that it is surely “sound from behind”. Such a sound image localization can be given.

  The sound image localization apparatus of this embodiment will be described with reference to FIGS. FIG. 1 shows a configuration at the time of reproduction of the sound image localization apparatus according to the present embodiment. FIG. 2 shows a detailed view of the configuration of the post-processing DSP 13 in the DSP 10.

First, the overall structure of the sound image localization apparatus will be described with reference to FIG.
The outline of the configuration of the sound image localization apparatus will be briefly described as follows. That is, the digital audio signal of the audio sources 23, 21, and 24 is captured, the DSP 10 performs digital processing on this signal, converts it to an analog audio signal with the D / A converter 22, and adjusts the volume with the electronic volume 41 The power amplifier 42 outputs this analog audio signal to the Lch speaker 11L and the Rch speaker 11R to emit sound.
The outline of the function of the sound image localization apparatus of the present embodiment will be briefly described. As shown in FIG. 1, 6-channel sound of Lch, Rch, Cch, LSch, RSch, SBCch (surround back center, SBCLch and SBCRch) is shown. The signal is mixed down to create a sound image localization as if four speakers, LSch, RSch, SBCLch, and SBCRch, are actually present from the front speakers 11L and 11R that are actually present in 2ch.
Further, the outline of the sound image localization means will be briefly described. In the DSP 10, among these 6-channel digital sound source data, the head-related transfer function from the rear to the human ear (for the rear side audio signal) Details will be described later). Furthermore, for SBC (SBCLch and SBCRch), the sound image localization of a pair of rear virtual speakers SBCL and SBCR in a diagonally rearward direction is “localized backward” using volume adjustment and phase difference. This is done by adding Then, these 6ch sound sources are processed and output from the existing speakers 11L and 11R using crosstalk cancellation (details will be described later) for delivering the sound image localization to both ears as they are. Hereinafter, these configurations will be described in order.

1 includes at least a DIR 23, an A / D converter 21, and an HDMI 24 (registered trademark, the same applies hereinafter). Each of these signal input units can input 6ch data. This 6ch will be described later.
The DIR 23 can input digital time-series audio data of a bit stream.
The A / D converter 21 can convert an analog signal, for example, a voice signal input from a microphone into digital time series data, and sends the data to the decoder 14.
HDMI 23 (High-Definition Multimedia Interface) receives audio and control signals together.
The DSP 10 includes a post-processing DSP 13 and a decoder 14. The DSP 10 processes the digital time series data input from the above-described input portion and sends it to the D / A converter 22.
The D / A converter 22 converts the data generated by the DSP 10 into an analog signal. This analog signal is converted into sound by the speakers 11L and 11R via an electronic volume 41 for adjusting the volume and a power amplifier.

  The power amplifier 42 may be a digital amplifier that turns on and off the switching element by a bit string without being converted into an analog signal by a D / A converter.

  As shown in FIG. 1, the 6-ch input that can be handled by the apparatus of this embodiment is a digital audio input that is output to Lch (front left), Rch, Cch, LSch, RSch, and SBC (SBCLch and SBCRch) speakers. In the real speaker system, the signals are output to the front left, front right, front center, side left, side right, and back center speakers, respectively. However, if one back center speaker is installed directly behind, the localization feeling moves forward as described above. Therefore, a back center left speaker and a back center right speaker are installed behind the left and right sides, respectively. The synthesized sound of the output sound from the speaker is localized at the back center. For this reason, the audio signal of SBCch (surround back center ch) is separated into SBCL and SBCR.

  On the other hand, in the virtual sound system of this embodiment, there are only front left and front right speakers, Lch is the output of the existing speaker on the left front side, and Rch is the output of the existing speaker on the right front side. is there. The speaker corresponding to the input of Cch does not actually exist in the apparatus of the present embodiment, but as shown in the DSP 10 of FIG. 1, the apparatus of the present embodiment distributes Lch and Rch and simply synthesizes and outputs. LSch, Rsch, and SBC (SBCLch and SBCRch) are audio inputs to the rear speakers. In the apparatus of the present embodiment, the corresponding speakers are fictitious, and perform signal processing in the DSP 10 to Lch and Rch. Synthesize. The reason for mixing down in this way is that it is not always practical to prepare a 6ch amplifier and speaker output system, so the apparatus of this embodiment uses the above-mentioned head-related transfer function or the like to output from the rear. Creates sound image localization and supplements the fictitious speaker output. At that time, SBCch (SBCLch and SBCRch) is set to the left and right rear virtual speakers SBCL and SBCR, and the sound image localization of these speakers is determined by using the volume adjustment filter and the phase adjustment filter. 2 is created (details will be described later in the description of FIG. 2).

  The sound image localization apparatus also includes a controller 32 that controls the above-described configuration, a memory 31 that stores control data of the controller 32, and a user interface 33 that instructs the controller 32. The memory 31 stores the model head-related transfer function as a data table from the direction in which each speaker is present to each ear. This model head-related transfer function is a filter function that simulates spatial propagation from a predetermined direction to the ear, and is already known as a database. By using this, it is possible to create a sound image localization as if the sound from the back is emitted. Here, each of the LS rear virtual speaker LSV and the RS rear virtual speaker RSV uses a model head-related transfer function corresponding to an angle in the range of 90 to 120 degrees to the left and right when viewed from the line of the face direction 103 of the listener. . The rear virtual speakers SBCLch and SBCRch use head-related transfer functions corresponding to angles in the range of 150 to 170 degrees to the left and right when viewed from the line of the listener's face direction 103. Note that crosstalk cancellation, which will be described later, also uses a head-related transfer function inverse filter or the like that simulates the propagation path from the front speaker to the ear.

Next, the DSP 10 (the rear localization adding unit 131, the crosstalk cancellation correction circuit 133, and the adders 135C and D will be described later in the description of FIG. 2) will be described in further detail with reference to FIG. The DSP 10 includes a decoder 14 and a post-processing DSP 13. Each will be described below.
The decoder 14 decodes the digital time-series data input from the DIR 23, the A / D converter 21 and the HDMI 24, which are the input parts, and sends them to the post-processing DSP 13. As described above, the decoder 14 itself can handle 6ch audio data as the digital time series data. That is, these 6ch are digital audio inputs to be output to the speakers of Lch, Rch, Cch, LSch, RSch, and SBCch (SBCLch and SBCRch).
The post-processing DSP 13 performs signal processing on these 6ch audio data, mixes them down to 2ch data, and outputs them as pseudo 6ch signals. The post-processing DSP 13 may be configured as software.

  In order to perform the mixdown as shown in FIG. 1, in the system of the present embodiment, Cch is first allocated to Lch and Rch, and adders 135A and 135B add to these Lch and Rch signals. This is because Cch is simply localized at the center only by the volume ratio of the left and right speakers 11L and 11R. Further, when downmixing is performed in this way, LSch, RSch, and SBCch (SBCLch and SBCRch) are required to localize the virtual speaker in the rear direction, and therefore include a rear localization adding unit 131 and a crosstalk cancellation correction circuit 133. ing. Then, as shown in FIG. 1, LSch and RSch audio signals are processed and added to Lch and Rch.

Hereinafter, the rear localization adding unit 131 will be described with reference to FIG. As described above, FIG. 2 shows a detailed view of the configuration of the post-processing DSP 13 in the DSP 10. The crosstalk cancellation correction circuit 133 will be described later.
As described above, the rear localization adding unit 131 as shown in FIG. 2 creates a virtual sound image localization feeling that can be heard from the rear side or the oblique rear side. The method will be described below.
First, the filters 131LD, LC, RC, and RD in the rear localization adding unit 131 will be described. Here, for easy description of these filters 131LD, LC, RC, and RD, LS rear virtual speaker LSV and RS rear virtual speaker RSV as shown in the right of FIG. Assume that the sound itself is emitted from the speakers LSV and RSV. With this assumption, the LSch sound enters the left ear M1 through the rear direct direction 102D and is transmitted to the right ear M2 through the rear cross direction 102C. In order to simulate this spatial transfer, the filter 131LD and the filter 131LC use the head-related transfer functions of the paths 102D and 102C, respectively. As described above, LSch has been described, but the RSch sound is also symmetrical with respect to the line of the listener's face direction 103 for the sake of explanation (the positional relationship may not be line symmetric). .

Here, the filter functions of the rear localization adding units 131LD, LC, RD, and RC of FIG. 2 are summarized as follows. The filter 131LD uses a head-related transfer function from the LS rear virtual speaker LSV to the left ear M1.
The filter 131LC uses a head-related transfer function from the LS rear virtual speaker LSV to the right ear M2.
The filter 131RD uses a head-related transfer function from the RS rear virtual speaker RSV to the right ear M2.
The filter 131RC uses a head-related transfer function from the RS rear virtual speaker RSV to the left ear M1.

  Further, as shown in FIG. 4, in the filters 131LD, LC, RD, and RC shown in FIG. 2, not only the head-related transfer functions shown above but also the delays D that take into account the time difference between these propagation paths are individually provided. Provided. Note that the amount d of the delay D is different for each of the filters 131LD, LC, RD, and RC.

  Then, the rear localization adding unit 131 in FIG. 2 adds the audio signals obtained by convolution of these filters into the LSch and RSch, and adds them in the LS rear localization calculation unit 131L and the RS rear localization calculation unit 131R, so that the rear virtual speaker LSV is added. RSV acoustic characteristics are added.

  The rear localization calculation units 131L and R in FIG. 2 add the audio signals that have been signal-processed by these filters of the rear localization addition unit 131. This addition method is an audio signal for the LS rear localization calculation unit 131L to generate a sound to be localized with the left ear, and an RS signal for the RS rear localization calculation unit 131R to generate a sound to be localized with the right ear. Equivalent to. Then, the crosstalk cancellation described later performs signal processing such that the signals calculated by the calculation units 131L and R are directly input to the left and right ears using the front 2ch speakers 11L and 11R. Note that the rear localization calculation units 131L and 131 in FIG. 2 also add the signals added by the rear localization calculation units 131SL and SR, which will be described later.

Next, the filter 131S in the rear localization adding unit 131 in FIG. 2 will be described. The purpose of the filter 131S is to input an SBCch that is an input signal corresponding to a rear speaker, and to create a sound image localization of “sounding from the rear” from the front two-channel speaker output.
As a means for this, the filter 131S includes filters 131SLD, SLC, SRC, and SRD that manipulate frequency characteristics that greatly contribute to the formation of a sense of localization in the front-rear direction of human hearing, and a volume that greatly contributes to the formation of a sense of localization in the left-right direction. Gain adjusting filters G1 and G2 and delay amount adjusting filters D1 and D2 that operate phase difference characteristics that greatly contribute to the formation of a sense of localization in the left-right direction. Then, the filter 131S performs signal processing by distributing one SBCch into four as shown in FIG.

  First, the filters 131SLD, SLC, SRC, and SRD in the filter 131S of FIG. 2 are the same as the filters 131LD, LC, RC, and RD, respectively. In other words, for SBCL, for the filters 131SLD and SLC, the LSch sound enters the left ear M1 through the rear direct direction 104D, and is transmitted to the right ear M2 through the rear cross direction 104C. In order to simulate, the filter 131LD and the filter 131LC use the head-related transfer functions of the paths 104D and 104C, respectively. Similarly, the filters 131SRC and SRD use a head-related transfer function that simulates a propagation path from the rear virtual speaker RDSB to both ears.

Here, the filter functions of the filters 131SLD, SLC, SRC, and SRD of FIG. 2 are summarized as follows.
The filter 131SLD uses a head-related transfer function from the rear virtual speaker SBCL to the left ear M1.
The filter 131 SLC uses a head-related transfer function from the rear virtual speaker SBCL to the right ear M2.
The filter 131SRD uses a head-related transfer function from the rear virtual speaker SBCR to the right ear M2.
The filter 131SRC uses a head-related transfer function from the rear virtual speaker SBCR to the left ear M1.

  Furthermore, as shown in FIG. 4, the filters 131 SLD, SLC, SRC, and SRD are individually provided with delays D that take into account not only the head-related transfer functions described above but also the time difference between these propagation paths. The amount d of the delay D is different for each of the filters 131SLD, SLC, SRC, and SRD.

  The gain adjustment filters G1 and G2 and the delay amount adjustment filters D1 and D2 in FIG. 2 will be described with reference to FIG. FIG. 3 is a diagram illustrating the concept of these functions. First, as described above, the filters 131SLD, SLC, SRC, and SRD simulate the spatial propagation of the propagation path from the SBCL and SBCR behind the “slanting” to both ears. Here, if the human auditory sense is not directly behind but obliquely behind, localization in the front-rear direction of the voice can be easily detected by the frequency characteristics. In the apparatus of the present embodiment, the volume ratio and the phase difference are further adjusted so that the sound image localization of the SBCL and SBCR obliquely rearward is drawn toward the rearward directions 105 and 106 shown in FIG. In other words, the volume ratio that greatly contributes to the formation of the left and right localization feeling and the phase difference based on the reach distance difference are used. For this adjustment, gain adjustment filters G1 and G2 and delay amount adjustment filters D1 and D2 are used.

Hereinafter, an adjustment method of the gain adjustment filters G1 and G2 and the delay amount adjustment filters D1 and D2 in FIG. 2 will be described. The gain adjustment filters G1 and G2 adjust the audio gain in the rear cross direction 104C to be smaller than the path in the rear direct direction 104D in FIG. 3 in order to attract the sound image localization in the rearward direction 106. Generally, the gain of the head-related transfer function is adjusted so that the gain level difference is small because the gain level is smaller than the direct direction due to the longer propagation distance in the cross direction. .
The delay amounts d1 and d2 of the delay amount adjusting filters D1 and D2 in FIG. 2 are provided in the filters 131SLD, SLC, SRC, and SRD described in FIG. 4 in order to attract the sound image localization in the backward direction 107. The delays D for adjusting the respective propagation time differences are adjusted so as to reduce the delay difference between the direct direction 107D and the cross direction 107C as shown in FIG.

  For the sake of explanation, delay filters are separately provided for the filters 131SLD, SLC, SRC, and SRD of FIG. 2 and also for the delay amount adjustment filters D1 and D2. However, in actual implementation, these delay amounts are added. Thus, it is convenient to process them all together. Further, the gain adjustment filters G1 and G2 are also conveniently stored as data in the memory 31 as filter coefficients of the filters 131SLD and SLC in actual implementation.

  As shown in FIG. 2, the rear localization calculators 131SL and SR add the audio signals signal-processed by these filters of the rear localization adding unit 131S. This addition method corresponds to an audio signal for the rear localization calculation unit 131SL to generate a sound to be localized with the left ear and a rear localization calculation unit 131SR to generate an audio signal to generate a sound image with the right ear. . The rear localization calculation unit 131L further adds the signal of the calculation unit 131SL, and the rear localization calculation unit 131R further adds the signal of the calculation unit 131SR and sends it to the crosstalk cancellation correction circuit 133.

The filter 131 described in FIG. 2 corresponds to a “rear localization addition filter” of the present invention.
In the apparatus of the present embodiment, as shown in FIGS. 2 and 3, the gains are adjusted by G1 and G2 for the filters 131LD and LC that create the sound image localization of the left rear virtual speaker SBCL, and the right rear virtual Although the delay amount is adjusted with respect to the filters 131RD and RC that create the sound image localization of the speaker SBCR, the left and right may be reversed. Further, for both the left and right SBCL and SBCR, only gain adjustment, only adjustment of the delay amount, or both may be used.

Hereinafter, the crosstalk cancellation correction circuit 133 of FIGS. 1 and 2 will be described. The purpose of the correction circuit 133 is to deliver the sound field itself created by the rear localization adding unit 131 to both ears. This is possible if the sound of the LS rear localization calculators 131L and 131R is listened to with ideal headphones (however, this is not necessarily the case because the headphones have characteristics with many peaks and dips). .)
However, in the apparatus of the present embodiment using a loudspeaker, since sound is heard from the front speakers 11L and 11R, it is deformed by spatial transmission from the front speakers 11L and 11R to both ears when transmitting sound waves in space. Therefore, there is a possibility that the effect of adding the LS rear orientation described above cannot be sufficiently exhibited.
Therefore, a sound source output from a real speaker existing in advance so that the output of the LS rear localization calculation unit 131L is only input to the left ear and the output of the RS rear localization calculation unit 131R is only input to the right ear in a pseudo manner. Is processed.

  Next, the method for obtaining the filter coefficient of the crosstalk cancellation correction circuit 133 described above with reference to FIG. 2 will be supplementarily described with reference to FIG.

The crosstalk cancellation correction circuit 133 in FIG. 2 uses a head-related transfer function that simulates the spatial transfer from the previous speakers 11L and 11R to both ears or is actually measured by an experiment. As described above, this head-related transfer function is stored as a data table in the memory 31 of FIG. The controller 32 selects an appropriate head-related transfer function from the data table stored in the memory 31 of FIG. 1 for (speakers 11L, 11R) vs. (left ear, right ear). Specifically, the following functions are selected and defined as follows for convenience of explanation. That is,
The transfer function of the path of (Lch speaker 11L → left ear) is represented by LD (Z),
The transfer function of the route of (Lch speaker 11L → right ear) is LC (Z),
The transfer function of the route of (Rch speaker 11R → left ear) is RC (Z),
The transfer function of the path of (Rch speaker 11R → right ear) is RD (Z),
(Each is a discrete domain and Z-transformed. Z represents delay. Hereinafter, “(Z)” is omitted.). If defined in this way, the transfer function LD, LC, RC, and RD filter functions of the Lch direct correction 133LD, the Lch cross correction 133LC, the Rch cross correction 133RC, and the Rch direct correction 133RD are obtained by calculating as follows. It is done.

  First, the sound heard by both ears transmits the output itself of the rear localization calculation unit 131 simulating the sound field of the rear rear virtual speakers LSV and RSV as shown in FIG. It is necessary to form a sound field.

Note that “≈” represents that the sound on the left side is equivalent when converted to an electrical signal by a microphone or the like (the same applies hereinafter).

  Next, the components transmitted from the rear to the ear are deformed by the acoustic environment around the head, and the outputs of the adders 135C and 135D are deformed by the head-related transfer functions from the front speakers 11L and 11R. Using the head related transfer functions LD, LC, RC, and RD, the following is considered to be transmitted.

This is because speech can be calculated by superposition.

Therefore, the audio signals to be output by the adders 135C and 135D in FIG. 2 are as follows.

From the above description, the digital data to be generated by the adder 135C and the adder 135D in FIG. 2 is digital data corresponding to the virtual rear speaker component of the sound obtained by this equation. Therefore, the transfer functions of the crosstalk cancellation correction circuit 133 are respectively
Lch direct correction is RD / (RD × LD-RC × LC),
Lch cross correction is LC / (RD × LD-RC × LC),
Rch cross correction is RC / (RD × LD-RC × LC),
Rch direct correction is LD / (RD × LD-RC × LC),
It becomes. Note that “x” represents convolution, and data obtained by convolving the Lch cross correction 133LC and the Rch cross correction RC is respectively multiplied by −1 and added by the adder 135C.

  As described above, the digital audio input that has passed through the crosstalk cancellation circuit 133 and the adders 135C and 135D in FIG. 2 is added to the Lch and Rch data by the adders 135A and 135B. The added data is output to the D / A converter 22 as 2ch data, and is converted into sound by the speakers 11L and 11R via the electronic volume 41 and the power amplifier.

  Note that the calculation of the crosstalk cancellation correction shown in the description of FIG. 2 described above is actually difficult due to the large number of time delay taps. Therefore, as an approximation of the practical range, canceling the influence of the cross direction by adding an inverse function of the head-related transfer function in the cross direction from the direct direction side is performed (for example, see Patent Document 1).

  The outline explanation briefly described at the beginning and the numerical values shown in the apparatus of the present embodiment do not limit the present invention, and other configurations are possible.

  Further, although the apparatus of the present embodiment includes crosstalk cancellation, the audio signal of the LS rear localization calculator 131L is directly input to the adder 135C, and the audio signal of the RS rear localization calculator 131R is directly added to the adder 135D. It is also possible to perform signal processing to be input to and listen with headphones. In this case, it is considered that the rear sound field calculated by the calculation units 131L and 131R can be input to both ears as it is. However, since headphones have many dips and peaks, a filter that corrects the frequency characteristics of the headphones may be required.

A configuration of a sound image localization apparatus according to this embodiment will be described. FIG. 2 shows a detailed diagram of a configuration of a post-processing DSP in the DSP of the sound image localization apparatus according to the present embodiment shown in FIG. 1. A conceptual diagram about gain adjustment filters G1 and G2 and delay amount adjustment filters D1 and D2 of a sound image localization device concerning this embodiment is shown. The block diagram of the sound image localization filter of the sound image localization apparatus which concerns on this embodiment is shown.

Explanation of symbols

10-DSP
13-post-processing DSP
131-rear localization 131LD-filter 131LC-filter 131RC-filter 131RD-filter 131L-LS rear localization calculator 131R-RS rear localization calculator 131S-filter 131SLD-filter 131SLC-filter 131SRC-filter 131SRD-filter 131SL-rear localization Calculation unit 131SR-Rear localization calculation unit 133-Crosstalk cancellation correction circuit 133LD-Lch direct correction 133LC-Lch cross correction 133RC-Rch cross correction 133RD-Rch direct correction 135A-adder 135B-adder 135C-adder 135D-addition 14-decoder 21-A / D converter 22-D / A converter 23-DIR
24-HDMI
31-memory 32-controller 33-user interface 41-electronic volume 42-power amplifier 100-listener (dummy head)
101D-forward direct direction 101C-forward cross direction 102D-rear direct direction 102C-rearward cross direction 103-listener face direction 104D-rear direct direction 104C-rearward cross direction 105-rearward direction 106-rearward direction 107D-rear direct direction 107C-rear cross direction 11L-Lch speaker 11R-Rch speaker LSV-LS rear virtual speaker RSV-RS rear virtual speaker SBCL-rear virtual speaker SBCR-rear virtual speaker M1-left ear M2-right ear D-delay D1, D2-delay adjustment filter G1, G2-gain adjustment filter

Claims (5)

A signal processing device including a rear localization addition filter that adds a rear virtual sound image localization to an audio signal output from outputs of two front real speakers,
The rear localization additional filter is:
A direct path simulation filter comprising a filter simulating a propagation path in a direct direction from a preset oblique rear position to a listener's ear near the position;
Cross path simulation filter consisting of a filter simulating the propagation path in the cross direction from the oblique rear position to the ear of the listener far from the position;
And a gain adjusting unit that is connected in series to at least one of these path simulation filters and has a filter characteristic set so that the gain levels of the pair of simulation filters approach each other. A signal processing device including a rear localization addition filter that adds a rear virtual sound image localization to an audio signal output from outputs of two front real speakers,
The rear localization additional filter is:
A direct path simulation filter comprising a filter simulating a propagation path in a direct direction from a preset oblique rear position to a listener's ear near the position;
Cross path simulation filter consisting of a filter simulating the propagation path in the cross direction from the oblique rear position to the ear of the listener far from the position;
A delay adjustment connected in series to at least one of the pair of simulated filters and having a filter characteristic so that a delay difference based on a difference in arrival time between the direct path and the cross path included in the pair of simulated filters approaches A signal processing apparatus. A signal processing device including a rear localization addition filter that adds a rear virtual sound image localization to an audio signal output from outputs of two front real speakers,
The rear localization additional filter is:
A direct path simulation filter comprising a filter simulating a propagation path in a direct direction from a preset oblique rear position to a listener's ear near the position;
Cross path simulation filter consisting of a filter simulating the propagation path in the cross direction from the oblique rear position to the ear of the listener far from the position;
A gain adjusting unit that is connected in series to at least one of these path simulation filters, and in which a filter characteristic is set so that the gain levels of the pair of simulation filters approach each other;
A delay adjustment connected in series to at least one of the pair of simulated filters and having a filter characteristic so that a delay difference based on a difference in arrival time between the direct path and the cross path included in the pair of simulated filters approaches A signal processing apparatus. The audio input signal to be input is a 2ch audio signal set for left and right diagonally backward directions,
The signal processing apparatus according to claim 1, further comprising the rear localization addition filter for each of the audio input signals. It has an input for inputting multi-channel audio signals,
4. The rear localization addition filter according to claim 1, wherein the rear localization addition filter includes the rear localization addition filter for each of two channels of a surround back center input signal as an audio input signal for the rear speaker. Signal processing device.

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