JP2006080709A - Audio reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an audio reproducing device capable of bringing out a surround effect while keeping a stereo feeling and the moving feeling of left and right sounds for stereo input signals at the time of headphone reproduction. <P>SOLUTION: In a surround sound field processing means, at the time of the headphone communication, the composite processing of the crosstalk components of channels with each other of the audio signals L Input Data and R Input Data of the respective channels is eliminated, and the surround sound field processing of the respective channels is executed by using direct sounds (head part transmission function H<SB>LL</SB>in an L side ear and head part transmission function H<SB>RR</SB>in a R side ear) from the speakers L Speaker and R Speaker of the respective channels to the ears (L side ear and R side ear) on the respective sides of a listener at a position assumed to be a listening position and the head part transmission functions (H<SB>LL1</SB>-H<SB>LL4</SB>in the L side ear and H<SB>RR1</SB>-H<SB>RR4</SB>in the R side ear) only for four reflection sounds from a wall surface 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an audio playback apparatus for playing back music data, and more particularly to a technique for surround sound field processing during headphone playback.

  Out-of-head sound localization by surround sound field processing in headphone playback of an audio playback device that plays back two-channel music data of left and right channels (Lch, Rch) recorded on a recording medium such as FM radio broadcast, compact disc, mini-disc, The head obtained by measuring the acoustic transfer characteristics from the sound source (speaker) to the listener's ears by actual measurement or simulation so that the sound can be heard from the left and right Lch and Rch speaker systems in front of the listener. This is generally realized by signal processing using a partial transfer function.

FIG. 6 is a simple image diagram of out-of-head sound image localization by the headphone reproduction, and H _LL , H _LR , H _RR , and H _RL are head-related transfer functions from the sound source to both ears. For example, the head-related transfer function _HLR indicates a head-related transfer function (H) from the left (L) speaker to the right ear (R).

  FIG. 7 is a diagram for explaining the contents of the signal processing. The audio signals L Output and R Output output from the left and right L and R of the headphone 1 can be expressed by the following equations (1) and (2). .

また、より精密なサラウンド音場処理手段では、図８に示されるヘッドホン再生による頭外音像定位の簡単なイメージ図及び図９に示されるそのＬ側耳の信号処理の内容を説明する図のように、Ｌ側耳に至る音として、左右のスピーカからの直接音（太い実線と破線）のみならず壁面２から反射して両耳に至る複数の（図８では４本）反射音（細い実線と破線）をも処理対象に加えることが多い（Ｒ側耳も同様）。

Further, in the more precise surround sound field processing means, as shown in FIG. 8, a simple image diagram of out-of-head sound image localization by headphone reproduction and a diagram explaining the contents of the signal processing of the L-side ear shown in FIG. As the sound reaching the L side ear, not only the direct sound from the left and right speakers (thick solid line and broken line) but also a plurality of (four in FIG. 8) reflected sound reflected from the wall surface 2 and reaching both ears (thin solid line and broken line) Is often added to the processing target (the same applies to the R-side ear).

  The following [Patent Document 1] is known as an audio reproduction apparatus that performs surround sound field processing including crosstalk component synthesis processing for out-of-head sound localization in headphone reproduction as described above.

Japanese Patent Laid-Open No. 9-65498

In the synthesis processing in line with the general reason of surround sound field processing, a crosstalk component in which the sound from the Lch speaker of the dotted line signal in FIG. 6 is heard from the R side ear and the cross in which the sound from the Rch speaker is heard from the L side ear. It is considered that the talk component (the second term on the right side of the above formulas (1) and (2)) needs to be considered. That is, in Expressions (1) and (2), R Input × H _RL is added to the left channel output L Headphone Out, and L Input × H _LR is added to R Headphone Out.

  However, in the headphone reproduction, in the synthesis process including the crosstalk component of the audio signal, sound is heard from both channels even if only one of the channels has an input signal. From the viewpoint of audibility, it has been proved by the inventor's test that the stereo sound becomes close to monaural sound, and the movement of the sound in the horizontal direction from right to left (left to right) is reduced (described later). (See FIG. 5 and its description paragraph).

  When listening with headphones, the process of synthesizing the crosstalk components of the audio signals of each channel, which was effective when listening with the speakers, is reversed, resulting in a loss of left-right spread of the sound during headphone playback. Conceivable.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an audio playback device that improves the sense of sound spread in the horizontal direction during headphone playback of the audio playback device.

In the surround sound field processing of the two-channel audio signals L Input and R Input, the present invention synthesizes the crosstalk components R Input × H _RL and L Input × H _LR between the audio signals R Input and L Input of each channel. In an audio reproduction apparatus comprising: a surround sound field processing means for performing processing; a reproduction output means for a speaker system of audio signals L Output and R Output subjected to surround sound field processing; and a reproduction output means for headphones 1.
The surround sound field processing means detects whether or not the reproduction of the audio signals L Output and R Output subjected to the surround sound field processing is reproduction by the headphones 1, and when detecting that the reproduction is the reproduction by the headphones 1. , The synthesis process of the crosstalk components R Input × H _RL and L Input × H _LR between the audio signals R Input and L Input of each channel is stopped, and the listening position from the speakers L Speaker and R Speaker of each channel is stopped. Head transmission of only the direct sound (thick solid line) reaching each ear (L side ear, R side ear) of the listener at the assumed position, or only the direct sound and the reflected sound from the wall surface 2 (thin solid line) (for the L-side _{ear, H LL,} H LL1 _{~H LL4} next, it is similar for R side ear.) function performs surround sound field processing for each channel using the By providing an audio reproduction apparatus according to claim bets, to solve the above problems.

  Since the audio playback device according to the present invention is configured as described above, the processing of the crosstalk component in the surround sound field processing is stopped (blocked) during headphone playback, so that the sound spreads in the horizontal direction (left and right). An excellent effect that the feeling becomes larger is obtained.

  Embodiments of an audio playback apparatus according to the present invention will be described with reference to the drawings. It should be noted that the description and explanation of parts other than the surround sound field processing unit of the audio playback apparatus equivalent to the conventional technology are omitted, and only the surround sound field processing means during headphone playback will be described in detail.

  FIG. 1 is a conceptual diagram for explaining the simplest signal processing example of the surround sound field processing means of the audio reproducing apparatus according to the present invention. FIG. 2 is a diagram for explaining the simplest signal processing contents of the surround sound field processing means according to the present invention. FIG. 3 is a conceptual diagram for explaining the best signal processing example of the surround sound field processing means of the audio reproducing apparatus according to the present invention. FIG. 4 is a diagram for explaining the contents (part) of the best signal processing example. FIG. 5 shows (a) a waveform of input data (music data) during headphone playback, (b) an output waveform when a synthesis process including a crosstalk component corresponding to the conventional FIG. 9 is performed, and the present invention. FIG. 5 is a comparison diagram of output waveforms when a synthesis process corresponding to FIG. 4 is performed.

In the surround sound field processing means shown in FIG. 1 or FIG. 2 (generally signal delay and synthesis processing by a DSP), the audio signals L Input Data and R Input Data of each channel that have been used for speaker playback during headphone playback are recorded. The cross-talk components R Input × H _RL and L Input × H _LR between the channels are stopped, and each side of the listener assumed to be the listening position from the speakers L Speaker and R Speaker of each channel is stopped. The surround sound field processing of each channel is performed using the head-related transfer function H _LL or H _RR for only the direct sound reaching the ear (L side ear, R side ear).

In the surround sound field processing means shown in FIG. 3 or FIG. 4, during headphone playback (detecting that output switching has been performed when the headphone jack is inserted into the plug, and detecting that playback is through headphones) ), The processing of synthesizing the crosstalk components between the channels of the audio signals L Input Data and R Input Data of each channel, which has been performed in the speaker reproduction, is stopped, and the listening position from the speakers L Speaker and R Speaker of each channel is stopped. A direct sound (a head-related transfer function H _{LL for} the L-side ear and a head-related transfer function H _{RR for} the R-side ear) of each side of the listener at the assumed position and the wall 2 four reflected sound each using HRTFs regarding only _(H RR1 _{to H RR4} is _H LL1 _{~H LL4,} R side ear at L side ear) channel And it has a configuration in which the surround sound field processing.

  FIG. 3 shows an example of signal lines that reach the L-side ear in a space that takes into account four left and right reflected sounds.

  Next, the output waveform (c) and the input waveform (a) when the surround sound field processing according to the present invention shown in FIGS. 3 and 4 in the portable audio playback device shown in FIG. 5 is performed during headphone playback. And the measured data of the output waveform (b) when the surround synthesis process including the normal crosstalk component is performed. It represents the passage of time from left to right.

  First, the input waveform (a) is a waveform in which the sound is moving from right to left, and the waveform change from Rch to Lch can be confirmed over time.

  Next, in the output waveform (b) of the conventional surround sound field processing, at the initial stage, there is a place where the waveform can be seen only in the Rch at the input, and there is a place where the waveform can be confirmed also in the Lch by combining the crosstalk components. I understand that. It can also be seen that the difference between the Lch and Rch output waveform levels is smaller than the input waveform. This means that there is less movement of the left and right sounds.

  Next, in the output waveform (c) of the surround sound field processing of the present invention, it can be seen that the sense of movement of sound to the left and right is maintained. It has been confirmed that the surround effect spreading to the left and right also appears in the sense of hearing.

  In this way, when playing back headphones, the left and right audio input signals are processed independently in the surround sound field processing, so the sound spreads while maintaining the sense of stereo and the movement of the left and right sounds for stereo input signals. The surround effect can be brought out. In addition, when different head-related transfer functions are used for monaural signals, a virtual stereo signal can be reproduced and a surround effect can be derived.

  In addition, the above configuration is an example of an audio reproduction apparatus including a speaker system such as an audio component that includes a reproduction output means for a speaker system for audio signals subjected to surround sound field processing and a reproduction output means for headphones. However, it goes without saying that the present invention is also possible with a portable type audio playback apparatus that is provided with an external output terminal for connecting an external speaker and normally assumes headphone playback (including earphone playback).

It is a conceptual diagram for demonstrating the simplest example of signal processing of the surround sound field processing means of the audio reproduction apparatus which concerns on this invention. It is a figure for demonstrating the content of the simplest signal processing of the said surround sound field processing means based on this invention. It is a conceptual diagram for demonstrating the best signal processing example of the surround sound field processing means of the audio reproduction apparatus which concerns on this invention. It is a figure for demonstrating the content (part) of the said best signal processing example. (A) waveform of input data (music data) at the time of headphone reproduction, (b) output waveform when performing a synthesis process including a conventional crosstalk component, and (c) a synthesis process according to the present invention. It is a comparison figure of the output waveform in the case. It is a simple image figure of the out-of-head sound image localization by the conventional headphone reproduction. It is a figure explaining the content of the signal processing by the conventional surround sound field processing means. It is a simple image figure of the out-of-head sound image localization by the headphones reproduction | regeneration by the conventional more precise surround sound field processing means. It is a figure explaining the content of the signal processing of the L side ear by the conventional more precise surround sound field processing means.

Explanation of symbols

1 Headphone
2 Wall H _LL Head direct transfer function from left speaker to left ear H _RR Head direct transfer function from right speaker to right ear H _LR Head direct head transfer function from right speaker to right ear of H _RL right speaker HRTF of the direct sound reaching the left ear from the function H _LL1 to H _LL4 head related transfer function H of the reflected sound reaching the left ear from the left loudspeaker _RL1 to H _RL4 extending from the right speaker to the left ear reflected sound Head related transfer function

Claims (1)

In surround sound field processing of a two-channel audio signal, surround sound field processing means for synthesizing cross-talk components between channels of the audio signal of each channel, and reproduction output of the audio signal subjected to surround sound field processing to the speaker system And an audio playback device comprising:
The surround sound field processing means detects whether or not the reproduction of the audio signal subjected to the surround sound field processing is reproduction by headphones, and when detecting that the reproduction is reproduction by headphones, the surround sound field processing means Only the direct sound from the speakers of each channel to the ears on each side of the listener at the position assumed to be the listening position, or the direct sound and the reflected sound from the wall are stopped. An audio reproducing apparatus that performs surround sound field processing of each channel using a head-related transfer function for only the channel.

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