JP5034694B2 - Sound image localization processor - Google Patents

Description

  The present invention relates to a sound image localization processing device, and more particularly, to a sound image localization processing device that can clarify a sense of localization and suppress occurrence of erroneous recognition of a localization position.

  As a process for localizing a sound image at an arbitrary position, a process of convolving a head related transfer function (HRTF) with a sound source signal (sound image localization process) is known (see, for example, Patent Document 1). The head-related transfer function is a function that represents a transfer characteristic of sound from the sound source position to the ear, and varies depending on the sound source position.

  The case where headphones are used will be described. When a sound image is to be localized at a certain position A, the sound image can be localized at the position A by convolving the head-related transfer function having the position A as the sound source position with the sound source signal.

  FIG. 4 is a diagram showing an example of a specific circuit configuration for performing sound image localization processing. The sound image localization filter shown in the figure is a filter that performs a process of convolving a head-related transfer function with a sound source signal. When performing sound image localization processing, this sound image localization filter is installed for each of the left channel and the right channel with respect to the input sound source signals of two channels. Convolve the head-related transfer function up to the ear. Further, the sound image localization filter installed for the right channel convolves the head-related transfer function from position A to the right ear. The sound image localization process is performed as described above.

  By the way, the head-related transfer function is inherently different depending on the listener's head shape, sound source type, reproduction environment, etc., but in a general environment, the head-related transfer function may not be changed according to these. Many. As a result, the sense of localization at the side and the rear may become unclear or misrecognition of the localization position may occur. This is a problem of sound image localization processing that has been conventionally recognized.

Patent Documents 2 and 3 disclose techniques for solving the above problems. In the technique of Patent Document 2, a time delay difference and an intensity difference are introduced between the left and right channels. The values of the time delay difference and the intensity difference are determined by the position to be localized. In the technique of Patent Document 3, an indirect sound (reflected sound or reverberation sound) from an oblique direction is added to a main sound that has been subjected to sound image localization processing and reproduced. This indirect sound differs depending on the localization position of the main sound.
JP 2000-236598 A Special table 2001-511995 gazette Japanese Patent Laid-Open No. 7-212897

  However, the technique described in Patent Document 2 has a problem that the amount of calculation increases and the amount of memory used also increases because an operation for adding a time delay difference or an intensity difference is required. Further, the technique described in Patent Document 3 also has a problem that the amount of calculation increases and the amount of memory used also increases because calculation for generating indirect sound is required.

  Accordingly, one of the objects of the present invention is to provide a sound image localization processing device that can clarify the lateral and rear localization feelings and suppress the occurrence of erroneous recognition of localization positions while suppressing an increase in the amount of calculation and memory usage. There is.

A sound image localization processing device according to the present invention for solving the above problems is a sound image localization processing device that performs sound source localization processing on a plurality of sound source signals, and receives input of the plurality of channel sound source signals, Sound image localization means for performing sound image localization processing to localize the sound source signal to a predetermined sound image localization position for each channel and outputting a sound image localization signal; and the sound image of the sound image localization signal output from the sound image localization means Addition means for adding the sound source signal to a sound image localization signal of at least one channel on the localization position side and outputting the signal.
According to this, since the sound source signal before performing the sound image localization processing is added to the channel output signal on the sound image localization position side, the channel output signal on the sound image localization position side is stabilized, and the lateral and rear localization feeling is obtained. Clarified. Moreover, occurrence of erroneous recognition before and after the localization position can be suppressed. Furthermore, these effects can be obtained simply by adding, and an increase in the amount of calculation and memory usage is suppressed.
In the above SL sound localization processing apparatus, the adding means, when the sound image localization position is behind the listener, it intends row the addition.

Further, in the sound image localization processing apparatus, the sound image localization means includes a sound image localization filter that is minimized in a channel to which the sound source signal is added by the addition means, and the addition means includes the sound image localization filter. The channel to which the sound source signal is not added may be configured to include a delay device and a sound image localization filter with a minimum phase.
According to this, the phase of the output signal of the channel and the phase of the sound source signal to be added can be substantially matched. Further, by providing a delay device, the phase difference between both ears can be maintained even when a filter having a minimum phase is used.

A sound image localization processing apparatus according to one aspect of the present invention is a sound image localization processing apparatus including a left channel and a right channel, receives an input of a sound source signal, and localizes the sound source signal to a predetermined sound image localization position. Left channel sound image localization means for performing a sound image localization process and outputting a left channel signal; and a left channel addition means for adding the sound source signal to the output signal of the left channel sound image localization means and outputting the signal A sound image localization means for right channel that receives an input of the sound source signal, performs a sound image localization process for localizing the sound source signal to the sound image localization position, and outputs a signal for the right channel; and the right channel sound image localization means Right channel adding means for adding the sound source signal to the output signal and outputting the sound source signal, and the left channel when the sound image localization position is on the left ear side of the listener. Control means for outputting the sound source signal to a channel addition means and outputting the sound source signal to the right channel addition means when the sound image localization position is on the right ear side of a listener. To do.
According to this, the selective output of the sound source signal to each channel adding means can be performed according to the positional relationship between the sound image localization position and the listener.

In the sound image localization processing apparatus, the control unit accepts an input of a distance between the sound image localization position and a listener, and the left channel addition unit or the right channel addition unit receives the input according to the received distance. The gain of the amplification means for amplifying the sound source signal to be output may be controlled.
According to this, gain control of the amplification means can be performed according to the distance between the sound image localization position and the listener.

  Embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a diagram showing a system configuration of a sound image localization processing apparatus 1a according to the first embodiment of the present invention. As shown in the figure, the sound image localization processing device 1a has a configuration for processing sound source signals of the left (L) channel and the right (R) channel, and a sound image localization filter 10L for sound source signal processing of the left channel. , An adder 20 and a headphone speaker 30L, and a delay unit 5, a sound image localization filter 10R, and a headphone speaker 30R for sound source signal processing of the right channel.

  The delay unit 5 and the sound image localization filters 10L and 10R receive sound source signals of respective channels from a sound source device (not shown), and sound images for localizing the sound source signals to predetermined sound image localization positions for each channel. It functions as sound image localization means for performing a localization process and outputting a sound image localization signal. In this embodiment, the sound image localization position is fixed to the left ear side of the listener's head (the same as the left side of the listener when the listener is facing forward).

  Specifically, in the left channel, the sound image localization filter 10L receives a sound source signal from the sound source device, and convolves the head-related transfer function from the sound image localization position to the left ear. In the right channel, the delay unit 5 first receives a sound source signal from the sound source device, gives an amount of delay determined by the sound image localization position, and outputs it to the sound image localization filter 10R. The sound image localization filter 10R convolves the sound source signal input from the delay unit 5 with the head-related transfer function from the sound image localization position to the right ear.

Here, the head-related transfer function and the sound image localization process will be described in detail. The head-related transfer function h _rθφL (t) from the position (r, θ, φ) on the spherical surface with the radius r centered on the listener's head to the left ear is an impulse sound from the position (r, θ, φ). It is an impulse response that is emitted and collected by a microphone placed in the left ear. The same _applies to the head-related transfer function h _rθφR (t) to the right ear.

When the sound image localization filters 10L and 10R _receive the input of the sound source signal g (t), the convolution integrals W _rθφL (t) and W _rθφR (t) are calculated by the equation (1), respectively, and the signals W _rθφL (t) And W _rθφR (t) are output (sound image localization processing).

_{Here, h} rθφLm (t) and _{h rθφRm} (t) is obtained by minimum phase the _{h rθφL} (t) and _{h rθφR} (t), respectively. That is, the sound image localization filters 10L and 10R perform the calculation of the above equation (1) using the head-related transfer function that is minimized in phase. The sound image localization filters 10L and 10R using the head-related transfer function having the minimum phase as described above are referred to as the filters having the minimum phase. Note that the sound image localization filters 10L and 10R may output W _rθφL (t) and W _rθφR (t), respectively, by digital filter processing.

  The minimum phasing is a process for minimizing the delay of the output signals of the sound image localization filters 10L and 10R. In the present embodiment, in particular, the shift between the phase of the output signal from the sound image localization filter 10L and the phase of the sound source signal added to the output signal is reduced by minimizing the phase of the sound image localization filter 10L. As a result, the possibility that the respective signals cancel each other out during the addition in the adding unit 20 is reduced.

  By the way, since the phase difference between the left and right output signals is minimized by minimizing the head-related transfer function, depending on the sound image localization position, the phase difference between the left and right output signals may be small. It may be necessary. For this reason, when using a filter with a minimum phase, depending on the sound image localization position, it is necessary to advance the phase of the output signal on the sound image localization position side compared to the phase of the output signal on the side other than the sound image localization position side. Become. The delay unit 5 delays the sound source signal on the side other than the sound image localization position (here, the right channel) by a delay amount corresponding to the sound image localization position (hereinafter referred to as a delay amount based on minimum phase). Realize phase shift.

The specific value of the delay amount based on the minimum phasing is as follows. That is, the difference between the delay time of the head-related transfer function h _rθφL (t) to the left ear and the delay time of the head-related transfer function h _rθφR (t) to the right ear is a delay based on the minimum phase. Amount. More specifically, the left-right difference in the peak position of the impulse response from the sound image localization position to each ear determined based on each head-related transfer function is the delay amount based on the minimum phase.

The adding unit 20 adds the sound source localization to the channel output signal on the sound image localization position side of the output signal (left channel output signal) of the sound image localization filter 10L and the output signal (right channel output signal) of the sound image localization filter 10R. It functions as an adding means for adding the sound source signals and outputting the signals without passing through the filter. In this embodiment, since the sound image localization position is on the left ear side of the listener's head, the adder 20 is provided in the left channel, and the sound source signal g (t) is _{added to} the output signal W _rθφL (t) of the sound image localization filter 10L. ) (The sound source signal before passing through the sound image localization filter 10L) is added, and a signal W _rθφL (t) + g (t) is output.

The headphone speaker 30L _{converts the} signal W _rθφL (t) + g (t) output from the adder 20 into a sound wave and outputs the sound wave. The headphone speaker 30R converts the signal W _rθφR (t) output from the sound image localization filter 10R into a sound wave and outputs the sound wave.

  As described above, the sound image localization processing device 1a adds the sound source signal before the sound image localization processing to the channel output signal on the sound image localization position side of the left channel output signal or the right channel output signal. Here, since the sound source signal before performing the sound image localization processing has the property of being localized right next to the ear, the channel output signal on the sound image localization position side is stabilized by the above, and the lateral and backward localization is performed. The feeling is clarified. Moreover, occurrence of erroneous recognition before and after the localization position can be suppressed. Furthermore, since these effects can be obtained simply by adding, an increase in calculation amount and memory usage is suppressed.

  In this embodiment, the sound image localization position is fixed to the left ear side of the listener's head. However, the sound image localization position is an arbitrary position on the left ear side or right ear side of the listener's head. The delay unit 5 and the adder unit 20 are respectively installed in the left and right channels, and the input source adder unit 20 for the sound source signal is appropriately switched according to the sound source localization position, and the adder unit 20 for inputting the sound source signal The delay amount of the delay device 5 of the channel on the side (sound image localization position side) is 0, and the delay amount of the delay device 5 of the opposite channel is the interaural delay amount determined according to the left and right head related transfer functions. Good.

[Second Embodiment]
FIG. 2 is a diagram showing a system configuration of a sound image localization processing apparatus 1b according to the second embodiment of the present invention. In the figure, the same components as those in the sound image localization processing device 1a are denoted by the same reference numerals as those in FIG.

  As shown in FIG. 2, the sound image localization processing device 1b includes a left channel and a right channel. A delay unit 5L, a sound image localization filter 10L (left channel sound image localization means), and an adder are used for processing a sound source signal of the left channel. 20L (left channel addition means), speaker 31L, and amplification section 40L, for delaying the right channel sound source signal, delay unit 5R, sound image localization filter 10R (right channel sound image localization means), addition unit 20R (right Channel adding means), a speaker 31R, and an amplifier 40R. The sound image localization processing device 1b further includes a crosstalk canceller 50 and a control unit 60.

  The sound image localization processing device 1a and the sound image localization processing device 1b are configured such that the sound image localization processing device 1b is installed in a living room or the like, while the sound image localization processing device 1a uses the headphones speakers 30L and 30R. The difference is that general speakers 31L and 31R are used. Due to this difference, the sound image localization processing device 1b needs to cancel the interference between channels. The crosstalk canceller 50 is provided for this purpose, and performs processing for canceling interchannel interference between the left channel and the right channel.

  In the sound image localization processing device 1a and the sound image localization processing device 1b, the sound image localization position is fixed to the left ear side of the listener's head in the sound image localization processing device 1a, but in the sound image localization processing device 1b, the sound image localization processing device 1b is fixed. It is also different in that can be switched to either the left ear side or the right ear side. Hereinafter, the sound image localization processing device 1b will be described in detail focusing on this difference.

  First, the control unit 60 determines a sound image localization position. This determination is preferably made based on user input. Here, both of the amplification units 40L and 40R are amplification means with variable gain. The control unit 60 outputs a sound source signal to the adding unit 20L together with the amplification units 40L and 40R when the determined sound image localization position is on the left ear side of the listener, and the determined sound image localization position is the right ear of the listener. Functions as a control means for outputting a sound source signal to the adder 20R.

  A specific example will be described. When the determined sound image localization position is on the left ear side of the listener, the control unit 60 sets the gain of the amplification unit 40L to 1 and sets the gain of the amplification unit 40R to 0. As a result, the output signal of the adder 20L is obtained by adding the output signal of the sound image localization filter 10L and the sound source signal, and the output signal of the adder 20R becomes the output signal itself of the sound image localization filter 10R. This result is the same as the processing result of the sound image localization processing device 1a described in the first embodiment.

  On the other hand, when the determined sound image localization position is on the right ear side of the listener, the control unit 60 sets the gain of the amplification unit 40L to 0 and sets the gain of the amplification unit 40R to 1. Thereby, the output signal of the adder 20L becomes the output signal itself of the sound image localization filter 10L, and the output signal of the adder 20R becomes the sum of the output signal of the sound image localization filter 10R and the sound source signal. This result is the same as the processing result when it is assumed that the adding unit 20 is moved to the right channel side in the sound image localization processing device 1a described in the first embodiment.

  The control unit 60 outputs the sound source signal to the addition unit 20L or the addition unit 20R as described above. Further, depending on the distance between the sound image localization position and the listener, the control unit 60 outputs to the addition unit 20L or the addition unit 20R. A process for controlling the gain of the amplification means for amplifying the sound source signal to be output (the one of the amplification sections 40L or 40R whose gain is not set to 0 by the above-described process) is also performed. Specifically, the control unit 60 controls the gain of the amplification unit between 0 and 1 so that the gain becomes closer to 0 as the distance is longer.

  The control unit 60 receives an input of the distance between the sound image localization position and the listener, and performs the gain control according to the received distance. This input is preferably a user input.

Further, the control unit 60 calculates a difference between the delay time of the head related transfer function h _rθφL (t) determined based on the determined sound image localization position and the delay time of the head related transfer function h _rθφR (t). Calculate the delay amount based on the minimum phase. Then, the calculated delay amount is set in the delay device that is not on the sound image localization position side of the delay devices 5L and 5R, and the delay amount 0 is set in the delay device on the sound image localization position side. The delay devices 5L and 5R delay the input sound source signal by a set delay amount, and output the delayed sound source signal to the corresponding sound source localization filter.

  As described above, according to the sound image localization processing apparatus 1b, the selective output of the sound source signal to each adder 20 can be performed according to the positional relationship between the sound image localization position and the listener. Further, the gain control of the amplification unit 40L or 40R can be performed according to the distance between the sound image localization position and the listener.

  Here, effects obtained when an experiment is performed using the sound image localization processing apparatus 1b will be described. FIG. 3 is a diagram for explaining the outline of this experiment. As shown in the figure, this experiment is performed on three points (that is, obliquely behind the listener) at angles θ = 120 °, 135 °, and 150 ° from the front of the listener on the horizontal plane including the ears of the listener. A sound is output from the speaker as the sound image localization position, and eight listeners actually listen and confirm. As a result of the experiment, 8 out of 8 listeners have a stable channel output signal on the sound image localization position side for any of the above three points, and the lateral and rear localization feelings are clarified. It was said that the effect of suppressing the occurrence of misrecognition was obtained. From the results of this experiment, it is clear that the effect of the sound image localization processing device 1a can be obtained at least in the range of 120 ° ≦ θ ≦ 150 °.

  Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and the present invention can of course be implemented in various forms without departing from the scope of the present invention. It is.

  For example, in each of the above embodiments, an example in which one left channel and one right channel are provided has been described. However, the present invention can also be applied to a case in which a plurality of left channels and right channels are provided. For example, in 5.1 channel surround, the left front channel and the left rear channel correspond to the left channel, and the right front channel and the right rear channel correspond to the right channel. In this case, there are a plurality of channel output signals on the sound image localization position side. Among them, a sound source signal may be added to all the output signals on the sound image localization position side and output, or only a part (for example, left rear) The sound source signal may be added to (channel only) and output.

  Further, in each of the above embodiments, the example in which the output signal of each channel is output from the speaker and can be directly listened to by the listener has been described, but the output signal of each channel is recorded on a recording medium, and later When played back by a playback device, the output signal of each channel read from the recording medium may be output from a speaker.

It is a figure which shows the system configuration | structure of the sound image localization processing apparatus concerning 1st Embodiment of this invention. It is a figure which shows the system configuration | structure of the sound image localization processing apparatus concerning 2nd Embodiment of this invention. It is explanatory drawing for demonstrating the effect acquired when experimenting using the sound image localization processing apparatus concerning 2nd Embodiment of this invention. It is a figure which shows the example of the concrete circuit structure for performing the sound image localization process concerning the background art of this invention.

Explanation of symbols

  1a, 1b Sound image localization processing device, 5, 5L, 5R delay unit, 10, 10L, 10R Sound image localization filter, 20, 20L, 20R adder, 30L, 30R Headphone speaker, 31L, 31R speaker, 40L, 40R Amplifier , 50 Crosstalk canceller, 60 control unit.

Claims (4)

A sound image localization processing device that performs sound image localization processing on a sound source signal of a plurality of channels,
Sound image localization means that receives input of the sound source signals of the plurality of channels, performs sound image localization processing for localizing the sound source signal to a predetermined sound image localization position for each channel, and outputs a sound image localization signal;
When the sound image localization position is behind the listener, the sound source signal is added to the sound image localization signal of at least one channel on the sound image localization position side of the sound image localization signal output from the sound image localization means and output. Adding means for
A sound image localization processing apparatus comprising: The sound image localization processing apparatus according to claim 1 ,
The sound image localization means includes a channel to which the sound source signal is added by the addition means and includes a sound image localization filter with a minimum phase, and a delay to a channel to which the sound source signal is not added by the addition means. And a sound phase localization filter having a minimum phase.
A sound image localization processing device characterized by that. A sound image localization processing device having a left channel and a right channel,
Sound image localization means for receiving a sound source signal, performing sound image localization processing for localizing the sound source signal to a predetermined sound image localization position, and outputting a signal for the left channel;
Left channel addition means for adding and outputting the sound source signal to the output signal of the left channel sound image localization means;
Right channel sound image localization means for receiving input of the sound source signal, performing sound image localization processing to localize the sound source signal to the sound image localization position, and outputting a right channel signal;
Right channel addition means for adding and outputting the sound source signal to the output signal of the right channel sound image localization means;
When the sound image localization position is on the listener's left ear side, the sound source signal is output to the left channel addition means, and when the sound image localization position is on the listener's right ear side, the right channel addition means Control means for outputting the sound source signal to
A sound image localization processing apparatus comprising: In the sound image localization processing apparatus according to claim 3 ,
The control unit receives an input of a distance between the sound image localization position and a listener, and amplifies the sound source signal output to the left channel addition unit or the right channel addition unit according to the received distance. Controlling the gain of the amplification means of
A sound image localization processing device characterized by that.

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