JP2010004430A - Acoustic signal reproduction apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide reproduction sound with a sense of spreading, while being 2ch audio signals and further even when an interval of loudspeakers is narrow, without being affected by an individual difference, acoustic characteristics and a viewing position than heretofore. <P>SOLUTION: The 2ch audio signals are each inputted from input terminals 1, 2, and difference signals (L-R) and (R-L) are generated by a difference signal generator 3. The difference signals are subjected to filter processing by filters 4-7 so as to localize a sound image in a predetermined direction, are added to the original audio signals by adders 17, 18 after adjusting predetermined delay times and amplitude levels through retarders 8-11 and coefficient units 12-15, and are outputted via output terminals 18, 19. Transfer characteristics of the filters 4-7 are controlled by a sound image localization direction control means 20 in such a way that a sound image localization direction is switched at intervals of 25ms to 70ms. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an audio signal reproduction apparatus and method that can provide a wide reproduction sound even if the distance between speakers is narrow, even though it is a 2ch audio signal.

  In a sound reproducing apparatus, a sound field signal reproducing apparatus intended to reproduce a reproduced sound with a high sense of presence with a simple configuration is disclosed in Patent Document 1, and the structure of the sound field signal reproducing apparatus is described. As shown in FIG. In FIG. 8, the sound field signal reproducing apparatus includes input terminals 101 and 102, a difference signal extractor 103, arithmetic circuits 104, 105, 106, and 107, delay units 108, 109, 110, and 111, and an addition. And 112 and 113 and speakers 114 and 115.

First, the difference between the two signals MR (t) and ML (t) input in the difference signal extractor 103 is obtained, and the output signal is obtained from the left and right sides of the listener 116 by FIR filtering processing in the arithmetic circuits 104 to 107. Or, the sound image is localized in the left and right rear. The outputs of the arithmetic circuits 104 to 107 are delayed by the delay times τ1 and τ2 by the delay units 108 to 111, respectively, and supplied to the adders 112 and 113. The adder 112 adds the output signals of the input terminal 102, the delay unit 108, and the delay unit 110 at an arbitrary ratio, and the adder 113 adds the output signals of the input terminal 101, the delay unit 109, and the delay unit 111 at an arbitrary ratio. The outputs are output to the speakers 114 and 115, respectively.
JP 7-336798 A

  As described above, the difference or sum of the input signals is obtained, the convolution operation for localizing the sound image in an arbitrary direction is performed by the arithmetic means, and the arbitrary addition rate is added to the input signal after an arbitrary time delay. In addition, by reproducing, it is possible to provide a sound field signal reproducing apparatus capable of reproducing a natural spread with a sense of presence with a simple system configuration.

  However, in the above-described conventional sound field signal reproduction device, since the process for localizing the sound image in an arbitrary direction is a fixed process, the effect cannot be exhibited unless the listener is physically fixed. In addition, there is a problem that the effect differs depending on the listener, so-called individual differences are large.

  The object of the present invention is to solve the above problems and provide a sound field signal reproducing apparatus capable of reproducing a natural and realistic spread with a simple system configuration even if there are listeners' movements and individual differences. There is to do.

  An acoustic signal reproduction device according to the present invention comprises: signal processing means for performing signal processing for localizing a sound image of the input sound signal in a predetermined direction on the input sound signal, and outputting the signal as a 2-channel output sound signal; The signal processing means includes sound image localization direction control means for controlling the direction in which the sound image is localized, and the sound image localization direction control means controls the sound image localization direction to change at a predetermined time interval. It is characterized by this.

  Further, there are a plurality of directions in which the signal processing means can localize the sound image of the input audio signal, and the sound image localization direction control means determines the direction in which the sound image is localized from the plurality of directions for the predetermined time. It is characterized in that it is controlled so as to change by sequentially selecting at intervals.

  Further, the predetermined time interval is a time interval slightly exceeding the duration of the Haas effect.

  Further, the predetermined time interval is 25 ms to 70 ms.

  Further, the sound image localization direction control means controls to change the direction in which the sound image is localized at random time intervals.

  Further, the sound image localization direction control means controls to change the direction in which the sound image is localized when the envelope of the input audio signal is below a predetermined level.

  Further, the input audio signal is a difference signal between two channel audio signals, and the signal processing means processes the difference signal with a predetermined transfer characteristic and adds the difference signal to each of the two channel audio signals. The sound image of the difference signal is localized in a predetermined direction.

  Further, the input audio signal is a 5.1 channel content surround signal or a 7.1 channel content surround signal.

  In the acoustic signal reproduction method of the present invention, the signal processing step of performing signal processing for localizing the sound image of the input sound signal in a predetermined direction on the input sound signal and outputting the signal as a 2-channel output sound signal And a sound image localization direction control step for controlling a direction in which the sound image is localized in the signal processing step, and in the sound image localization direction control step, control is performed so as to change the direction in which the sound image is localized at a predetermined time interval. It is characterized by doing.

  As described above in detail, according to the acoustic device of the present invention, a spectrum cue characteristic corresponding to a plurality of angles is selected for the difference signal between each channel, processed, and reproduced. However, even if the distance between the speakers is narrow, and there are movements of the listener and individual differences, it is possible to provide a wide reproduction sound.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing the configuration of the acoustic apparatus according to Embodiment 1 of the present invention. In FIG. 1, 1 and 2 are input terminals, 3 is a difference signal generator, 4, 5, 6, and 7 are filters, 8, 9, 10, and 11 are delay units, 12, 13, 14, and 15 are coefficient units, Reference numerals 16 and 17 denote adders, reference numerals 18 and 19 denote output terminals, and reference numeral 20 denotes sound image localization direction control means for switching the characteristics of the filters 4 to 7.

  FIG. 2 is a diagram showing a route from the sound source to the listener for explaining the operation of the first embodiment. FIGS. 3 and 4 are diagrams of the sound source for explaining the operation of the first embodiment. FIG. 5 is a graph showing a sound pressure frequency characteristic from a sound source to a listener's pinna with respect to an angle, and FIG. 5 is an explanatory diagram for explaining the operation of the filter in the first embodiment. The operation of the first embodiment of the present invention will be described using the above drawings.

  In FIG. 1, an Lch input signal and an Rch input signal, which are 2ch audio signals, are input from input terminals 1 and 2, respectively, and a difference signal generator 3 outputs difference signals (L−R) and (R−L). ) Is generated. The difference signal is subjected to filter processing so that the sound image is localized in a predetermined direction by the filters 4 to 7, is delayed by a predetermined delay time by the delay units 8 to 11, and is amplified by the coefficient units 12 to 15. Are added to the Lch input signal and the Rch input signal by the adders 16 and 17 and output through the output terminals 18 and 19.

  By taking the difference between the 2ch audio signals, the components added at the same homologous level to both channels (components localized at the center of both channels, eg, vocals in pop music) are canceled out. Components with high correlation become weak, and components unique to each channel remain. It is known that there are many cases where such components are mainly reverberation components.

  On the other hand, the filters 4 to 7 are for localizing the sound image in a specific direction. FIG. 2 shows that the distance between the listener and the sound source is the same, and the path of the signal arriving from the sound source in the listener's pinna is different when the presentation angle of the sound source viewed from the listener is different. . When there is a sound source next to the sound source, the sound wave reaches the ear in a form that bypasses the human body (along the human body) to the ear opposite to the sound source side. In FIG. 2, the drawing is performed without including the reflected wave generated in the room (wall, floor, ceiling).

  3 and 4, the sound source was placed at various angles as shown in FIG. 2, and the transmission characteristics (frequency characteristics) of the sound waves actually arriving at the listener's auricle (right ear) at the listening point were measured. An example of the measurement result is shown. As can be seen from FIG. 3, it can be seen that the frequency characteristics vary greatly depending on the presentation angle of the sound source due to the influence of the listener's body (particularly the head and pinna shape and its position).

  Using the fact that the frequency characteristics vary depending on the presentation angle of the sound source as shown in FIG. 3, filtering so as to have the frequency characteristics of the angle at the sound source (the impulse response is obtained based on this frequency characteristic and convolved with the sound source) The sound image is localized as if the sound source exists from an angle different from the actual presentation position of the sound source.

  In the present embodiment, a difference signal including a component that forms a sound field feeling is generated from the 2ch audio signal, and the left and right (angle at which a 2ch stereo signal is normally presented: normal speakers of both channels) is generated with respect to the difference signal. A frequency characteristic is applied for sound image localization in a direction in which the feeling of spread is emphasized (for example, the horizontal direction to the horizontal rear direction: about 110 degrees to 135 degrees) than the opening angle of about 45 degrees to 60 degrees.

  Specifically, as shown in FIG. 5, the localization direction is obliquely rearward, and the left and right sound image localization positions are a sound source L and a sound source R. A transfer characteristic reaching the right ear from the sound source L is a filter LR, a transfer characteristic reaching the left ear from the sound source L is a filter LL, a transfer characteristic reaching the right ear from the sound source R is a filter RR, and a transfer characteristic reaching the right ear from the sound source R The transfer characteristic is a filter RL, the delay characteristic for controlling the arrival time difference due to the path difference from each sound source to both ears is the delay unit LL, the delay unit LR, the delay unit RL, and the delay unit RR, and the coefficient of each coefficient unit is Assuming coefficient 1, coefficient 2, coefficient 3, and coefficient 4, the output of each channel is as follows.

Lch output = Lch + (filter LL / delay device LL / coefficient 1-filter RL / delay device RL / coefficient 2) / (LR)
Rch output = Rch + (filter RR / delay device RR / coefficient 3-filter LR / delay device LR / coefficient 4) / (RL)
In this way, the difference signal of both channels including the reverberation component is localized at a position different from that of the actual speaker and added to the original signal for reproduction, so that there is a sense of spread regardless of the 2ch signal. It can provide highly realistic playback sound.

  By the way, it is a human being who views the musical sound reproduced at the listening point. Therefore, it is basically impossible to view for a long time with the posture fixed at the listening point. Furthermore, assuming a viewing style such as an actual television, it is generally considered that the viewing is far away from the vicinity of the listening point (for example, at first, sitting on a chair and watching in a certain sense is fixed to the listening point) It means that it is greatly deviated from the initial listening point, such as losing posture, lying down, etc.).

  If the filters 4 to 7 have a transfer characteristic at a fixed listening point, deviating from the initial listening point in this way will deviate from the sense of direction given when a sense of breadth is added. It is conceivable that side effects such as a feeling of spaciousness that was originally desired cannot be obtained, and an unpleasant sound quality due to the added frequency characteristic is emphasized to give a sense of spaciousness. Further, the characteristics of the filters 4 to 7 are influenced by individual differences because they are affected by the physical shape of the human body. Furthermore, since the reproduction space has various acoustic characteristics due to its shape, standing wave, reflected wave, etc., the effect of the feeling of spaciousness is also affected.

  Therefore, in this embodiment, instead of fixing the filter characteristic used for sound image localization processing in a specific direction that generates a feeling of spread to one, by switching and selecting from a plurality of filter characteristics under a certain condition, It suppresses the reduction in the effect of spaciousness caused by individual differences, acoustic characteristics of the playback space, and listening style. The sound image localization direction control means 20 controls this switching.

  Specifically, a filter characteristic in the direction of the design target and a filter characteristic in the vicinity of that direction are prepared to increase the sense of spread. That is, if the design target is, for example, 120 degrees, filter characteristics corresponding to a direction corresponding to several points (for example, in increments of 5 degrees) from a direction having a width of about ± 20 degrees centering on 120 degrees are prepared. .

  Then, selection switching is performed according to a predetermined condition from the plurality of prepared filter characteristics. The switching conditions will be described.

  In the first embodiment, the selection is switched every predetermined time interval (25 to 70 ms). Humans have what is called the Haas effect (preceding sound effect), and it is said that the effect lasts for about 25 to 35 ms. For this reason, in this embodiment, the filter characteristics are selectively switched at a time interval (for example, 40 ms) exceeding the duration of the hearth effect, so that there is no sense of incongruity due to switching, and one filter is selected and switched. Compared with the characteristics, it is possible to suppress the reduction in the effect of spreading due to individual differences, acoustic characteristics of the reproduction space, and listening styles.

(Haas effect)
The Haas effect is also called a precedence sound effect, and is one of the human psychoacoustic phenomena that correctly distinguishes the direction of a sound source that reaches both ears at different timings. Due to the geometrical structure of the head (the two ears are spaced apart and separated by a barrier), the sound from any sound source reaches the ear closer to the sound source, The far ears have a lower level or a delayed arrival time. Then, the human recognizes the presentation position of the sound source by the direction of the sound that first reaches the ear. However, even if a sound source is presented from a different direction within 25 to 35 msec (with individual differences) after recognizing the direction, a phenomenon that does not recognize that there is a sound source (even if the volume level is 10 dB higher) in that direction. There is. This is the Haas effect.

  As described above, according to the first embodiment of the present invention, a difference signal between input signals is generated, and transfer characteristics corresponding to a plurality of angles are generated in a difference signal between each channel so that the hearth effect is maintained. Even if it is a 2ch audio signal, even if the interval between the speakers is narrow, and there are movements of the listener and individual differences, by selecting and processing at a time interval slightly exceeding the time, and playing it back , It has the effect of providing a wide reproduction sound.

  In the first embodiment of the present invention, the difference signal of both channels is localized at a position different from that of the actual speaker and added to the original signal and reproduced (with the speaker). It goes without saying that the same effect can be obtained by combining (adding) in the acoustic space using the speaker.

  In the first embodiment of the present invention, the 2ch signal has been described. However, if a 5.1ch surround signal is input instead of the difference signal of the 2ch signal, the 5.1ch content becomes a surround speaker. Needless to say, a 5.1 channel surround effect can be obtained without providing a separate channel.

  Furthermore, in the case of 7.1ch content, two sets of surround signals (usually a surround back signal added later in addition to a 5.1ch surround signal is usually added), respectively. It goes without saying that by processing instead of the difference signal, a 7.1ch surround effect can be obtained without separately providing a surround speaker.

(Embodiment 2)
Next, the operation of the second embodiment will be described. The second embodiment is different from the first embodiment in that the filter characteristics that form a feeling of spreading are switched at random times (in the range of 25 to 70 msec).

  As in the first embodiment, the filter characteristics are selectively switched when the duration of the hearth effect is slightly exceeded, but in order to make the switching effect more effective, the timing for selecting and switching the filter characteristics is not fixed, Make it random. By making it random, it is possible to absorb the individual differences in the hearth effect and to absorb the change in the hearth effect duration due to the fluctuation in the level of the reproduction signal.

  As described above, according to the second embodiment of the present invention, a difference signal between input signals is generated, and transfer characteristics corresponding to a plurality of angles are selected at random time intervals as a difference signal between each channel. By processing and playing back, even if it is a 2ch audio signal, even if the distance between the speakers is narrow, or even if there are movements of the listener or individual differences, a wide reproduction sound can be produced. It has an effect that can be provided.

(Embodiment 3)
Next, the operation of the third embodiment will be described. The third embodiment is different from the first embodiment in that a filter characteristic that forms a sense of spread is selected and processed according to a change in the envelope level of the output signal of the difference signal generating means.

  FIG. 6 shows a block diagram of the configuration of the acoustic device according to the first embodiment. Compared with FIG. 1, the sound image localization direction control means 20 is controlled by the output of the difference signal generator 3.

  FIG. 7 is an explanatory diagram for explaining the operation of the third embodiment. The operation of the filter switching timing is to determine whether the envelope of the input signal of the filter is equal to or higher than a predetermined level. If the level is equal to or lower than the predetermined level, the filter is switched at a timing of, for example, every 40 msec, as in the first embodiment. → B → C → B → A → B... The filter is not switched during a period when the envelope is equal to or higher than a predetermined level.

  By switching the filter characteristics as described above, it is possible to absorb the change in the hearth effect duration due to the fluctuation in the level of the reproduction signal.

  As described above, according to the third embodiment of the present invention, a difference signal between input signals is generated, transfer characteristics corresponding to a plurality of angles are generated in the difference signal between each channel, and the level of the difference signal is set. By selecting and processing according to the sound, it is a 2ch audio signal, and even if the distance between the speakers is narrow, or there are movements of the listener and individual differences, It has the effect of providing a certain playback sound.

  The acoustic device according to the present invention is useful for providing a wide reproduction sound even if the distance between the speakers is narrow, and there are movements of individuals and individual differences, even though it is a 2ch audio signal. is there.

The block diagram which shows the structure of the acoustic signal reproducing | regenerating apparatus in Embodiment 1 of this invention. The figure which shows the path | route from a sound source to a listener for demonstrating operation | movement of Embodiment 1 of this invention. The graph which shows the sound pressure frequency characteristic from the sound source to a listener's auricle part with respect to the angle (45 degree-180 degree | times) of a sound source for demonstrating operation | movement of Embodiment 1 of this invention. The graph which shows the sound pressure frequency characteristic from the sound source with respect to the angle (180 degrees-315 degrees) of a sound source to a listener's pinna part for demonstrating operation | movement of Embodiment 1 of this invention. Explanatory drawing explaining operation | movement of the filter in Embodiment 1 of this invention. The block diagram which shows the structure of the acoustic signal reproducing | regenerating apparatus in Embodiment 3 of this invention. Explanatory drawing of operation | movement of the audio equipment in Embodiment 3 of this invention. The block diagram which shows the structure of the sound field signal reproduction apparatus of a prior art

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Input terminal 3 Difference signal generator 4-7 Filter 8-11 Delay device 12-15 Coefficient unit 16, 17 Adder 18, 19 Output terminal 20 Sound image localization direction control means

Claims (9)

Signal processing means for performing signal processing for localizing a sound image of the input sound signal in a predetermined direction with respect to the input sound signal, and outputting the signal as a 2-channel output sound signal;
Sound signal localization direction control means for controlling the direction in which the signal processing means localizes the sound image;
The sound image reproduction apparatus according to claim 1, wherein the sound image localization direction control means controls so as to change a direction in which the sound image is localized at a predetermined time interval. There are a plurality of directions in which the signal processing means can localize the sound image of the input audio signal,
The sound image localization direction control means controls to change the direction in which the sound image is localized by sequentially selecting the direction from the plurality of directions at the predetermined time interval. Acoustic signal reproduction device. 2. The acoustic signal reproducing apparatus according to claim 1, wherein the predetermined time interval is a time interval slightly exceeding a duration of the Haas effect. The acoustic signal reproducing apparatus according to claim 1, wherein the predetermined time interval is 25 ms to 70 ms. 2. The acoustic signal reproducing apparatus according to claim 1, wherein the sound image localization direction control means controls the sound image localization direction to change at random time intervals. 2. The sound signal reproduction apparatus according to claim 1, wherein the sound image localization direction control means controls the direction in which the sound image is localized so as to change when the envelope of the input audio signal is a predetermined level or less. . The input audio signal is a difference signal between two channel audio signals;
The signal processing means processes the difference signal with a predetermined transfer characteristic and adds it to each of the two-channel audio signals to localize the sound image of the difference signal in a predetermined direction. The acoustic signal reproducing apparatus according to claim 1. 2. The acoustic signal reproducing apparatus according to claim 1, wherein the input audio signal is a surround signal of 5.1 channel content or a surround signal of 7.1 channel content. A signal processing step of performing signal processing for localizing a sound image of the input sound signal in a predetermined direction with respect to the input sound signal, and outputting as a 2-channel output sound signal;
A sound image localization direction control step for controlling a direction in which the sound image is localized in the signal processing step;
In the sound image localization direction control step, the sound signal reproduction method is characterized in that the sound image localization direction is controlled to change at a predetermined time interval.

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