JP2013074459A - Acoustic reproduction system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acoustic reproduction system equipped with a directional characteristic control unit for controlling the directivity of speakers, which reproduces two independent sound signals in such a way that at the front position of a speaker reproducing one side of the sound signals, the reproduction level of the other side of the sound signals is extremely lowered and information derived from the one side of the sound signals is made easily audible.SOLUTION: The acoustic reproduction system includes a directional characteristic control unit which includes a first filter circuit, a second filter circuit, a first adder which adds a first sound signal and the phase inverted output of the second filter circuit, and a second adder which adds a second sound signal and the phase inverted output of the first filter circuit. The output signal of the first adder is forwarded to a first speaker, and the output signal of the second adder is forwarded to a second speaker. The first and the second filter circuits have transfer function characteristics substantially equal to the 90-degree direction directional characteristics referenced to the axial front surface direction sound pressure characteristics of the first and the second speakers.

Description

  The present invention is an acoustic reproduction device including a directivity control unit for controlling the directivity of a speaker. When reproducing two independent audio signals, the sound reproduction device is provided at the front position of the speaker that reproduces one of the audio signals. The present invention relates to an acoustic reproduction apparatus in which the reproduction level of the other audio signal is extremely low and information from the other audio signal can be easily heard.

  As a method of controlling the change in acoustic radiation characteristics depending on the direction (hereinafter referred to as “directivity”) using a speaker that reproduces sound waves in the audible sound range, two non-directional speakers are connected in opposite phases and are bidirectional. For example, a method of providing a unidirectional or directional beam in a certain direction by using three or more speaker arrays has been proposed. For example, the applicant has proposed a directivity control device capable of obtaining a clear unidirectional radiation characteristic only by using two speakers and a gaming machine using the directivity control device (Patent Document 1). Specifically, in this directivity control device, the input signal is delayed by a time corresponding to the separation distance of the two speakers and output, and the sound signal from the sound source and the delay means are delayed. Phase inversion means is provided so that the acoustic signals are acoustically radiated from the two speakers in opposite phases to each other.

  In the conventional method, the desired directivity is realized by applying a time delay to each speaker basically by the structure of the speaker and signal processing and utilizing the spatial phase interference of sound waves. In particular, when unidirectionality is realized, a direction in which the volume is reproduced at a high level (referred to as “beam direction”) and a direction in which the sound is reproduced at a low level (referred to as “zero point direction”) are generated. A sound reproduction system using the sound has been proposed. In this case, the area in the beam direction is normally used as an area where the listener is located, and the area in the zero point direction is mainly used for the purpose of lowering the volume.

  Further, conventionally, a first speaker, a second speaker, and a control means for radiating a sound wave from the first speaker to cancel a sound wave radiated from the second speaker by interference between sound waves. A speaker device comprising: the speaker device, wherein the first and second speakers are arranged at intervals of 1 wavelength or less and 1/8 wavelength or more of a frequency range of a sound wave to be controlled. (Patent Document 2). In addition, conventionally, two speakers that are juxtaposed at an interval of 1/8 wavelength to 1 wavelength of sound waves in the frequency domain of an acoustic signal and emit sound waves including the acoustic signal component, an acoustic signal source, and one speaker In the listening space for both speakers, a filter for canceling the sound wave emitted from both speakers by the interference of the sound waves, and a filter coefficient of the filter for changing the position where the sound wave is canceled There is a directional loudspeaker characterized in that it comprises a filter coefficient changing means for changing the above (Patent Document 3).

  However, in the prior art of Patent Document 1, since a constant delay time is given to all frequency components, a sharp dip occurs when the distance between two speakers is relatively longer than the wavelength of a sound wave to be reproduced. There is a problem that a good unidirectional characteristic cannot be obtained at that frequency. In the prior art of Patent Document 2 or 3, the distance between two speakers is limited with respect to the wavelength of the sound wave to be reproduced. There is a problem in that it is difficult to obtain a substantially good unidirectional characteristic because a speaker for the sound range must be prepared separately. If the unidirectional characteristics cannot be realized, the playback level in the zero point direction increases, so that the other audio signal can be heard superimposed on one audio signal, and even when two independent audio signals are reproduced, There is a problem that it becomes difficult to hear information by an audio signal.

JP 2003-87888 A (FIGS. 1 to 7) Japanese Patent No. 3422247 (FIGS. 1 to 3) Japanese Patent No. 3422281 (FIGS. 1 to 5)

  The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is an acoustic reproduction device including a directivity control unit for controlling the directivity of a speaker, and is independent of the above. When reproducing two audio signals, an audio reproduction device is provided that makes the reproduction level of the other audio signal extremely low at the front position of the speaker that reproduces one of the audio signals, and makes it easy to listen to information from one audio signal. There is to do.

  The sound reproducing device of the present invention includes a first speaker mounting surface, a cabinet portion including a second speaker mounting surface configured to be orthogonal to the first speaker mounting surface, and a first speaker mounted on the first speaker mounting surface. And a second speaker having the same configuration as the first speaker mounted on the second speaker mounting surface, and a directivity control unit that drives the first speaker and the second speaker to obtain a unidirectional radiation characteristic. The control unit adds the first filter circuit that filters the first audio signal, the second filter circuit that filters the second audio signal, and the first audio signal and the phase inversion output of the second filter circuit. 1 adder, and a second adder that adds the second audio signal and the phase-inverted output of the first filter circuit, and outputs the output signal of the first adder to the first speaker. The output signal of the second adder is output to the second speaker, and the first filter circuit and the second filter circuit are in the direction of 90 degrees with reference to the axial frontal sound pressure characteristics of the first speaker and the second speaker. It has transfer function characteristics substantially the same as the directivity characteristics.

  Preferably, in the sound reproducing device of the present invention, the first speaker and the second speaker are elongated electrodynamic speakers whose length in the minor axis direction is shorter than that in the major axis direction. The speakers are arranged so that the major axis directions thereof are parallel and the minor axis directions substantially coincide with each other, and the distance between the first speaker and the second speaker and the minor axis direction length are arranged close to each other. ing.

  Preferably, in the sound reproduction device of the present invention, the first audio signal and the second audio signal input to the directivity control unit are independent audio signals that are uncorrelated with each other.

  Preferably, in the sound reproduction device of the present invention, the directivity control unit is canceled by the distance between the first speaker and the second speaker, and the level of the low frequency region of the first signal or the second signal is canceled. It further includes compensation means for relatively increasing.

  Preferably, in the sound reproducing device of the present invention, the directivity control unit is configured such that the volume level of the output signal of the second filter circuit input to the first adder or the first filter circuit input to the second adder. Further included is a level adjustment circuit that adjusts and outputs the volume level of each output signal.

  Preferably, in the sound reproduction device of the present invention, the directivity control unit has a first delay circuit that delays the first audio signal input to the first adder, and a second audio signal input to the second adder. A second delay circuit for delaying the delay time, and the set delay times of the first delay circuit and the second delay circuit are made to coincide with the delay time of the transfer function characteristic.

  The operation of the present invention will be described below.

  The sound reproducing device of the present invention includes a first speaker mounting surface, a cabinet portion including a second speaker mounting surface configured to be orthogonal to the first speaker mounting surface, and a first speaker mounted on the first speaker mounting surface. And a second speaker having the same configuration as the first speaker mounted on the second speaker mounting surface, and a directivity control unit that drives the first speaker and the second speaker to obtain unidirectional radiation characteristics, and is independent When reproducing two audio signals, the sound reproduction device is capable of easily listening to information by one audio signal because the reproduction level of the other audio signal is extremely low at the front position of the speaker reproducing one audio signal. . For example, the first speaker mounting surface and the second speaker mounting surface of the cabinet portion may be configured from two adjacent surfaces of a rectangular parallelepiped as long as they are arranged and configured in a positional relationship orthogonal to each other.

  The directivity control unit adds the first filter circuit for filtering the first audio signal, the second filter circuit for filtering the second audio signal, and the first audio signal and the phase inversion output of the second filter circuit. And a second adder that adds the second audio signal and the phase-inverted output of the first filter circuit. The directivity control unit outputs the output signal of the first adder to the first speaker, and outputs the output signal of the second adder to the second speaker. Further, in the directivity control unit, the first filter circuit and the second filter circuit have substantially the same transfer function characteristics as the 90-degree direction directivity characteristics based on the axial front direction sound pressure characteristics of the first speakers and the second speakers. Have The directivity control unit further includes a first delay circuit that delays the first audio signal input to the first adder, and a second delay circuit that delays the second audio signal input to the second adder. In addition, the set delay times of the first delay circuit and the second delay circuit may be matched with the delay time of the transfer function characteristic.

  The sound reproducing device of the present invention includes a directivity control unit that reflects the configuration of the speakers in the cabinet unit (the first speaker, the second speaker, and the first speaker mounting surface and the second speaker mounting surface). Unidirectional radiation characteristics can be realized. That is, with respect to the first audio signal, the sound wave radiated from the first speaker and the sound wave radiated from the second speaker after being subjected to a transfer function characteristic substantially the same as the 90-degree direction directivity and being phase inverted. A unidirectional acoustic radiation characteristic is realized in which the front direction of the second speaker mounting surface on which the second speaker is mounted is the zero point direction. Similarly, for the second audio signal, a sound wave radiated from the second speaker, a sound wave radiated from the first speaker after being subjected to a transfer function characteristic substantially the same as the 90-degree direction directivity and phase-inverted, Thus, a unidirectional acoustic radiation characteristic is realized in which the front direction of the first speaker mounting surface on which the first speaker is mounted is the zero point direction.

  As a result, in the unidirectional zero point direction, the other audio signal is hardly superimposed on one audio signal so that it cannot be heard. Is easier to listen to. When the first audio signal and the second audio signal input to the directivity control unit are independent audio signals that are uncorrelated with each other, the other audio signal whose reproduction level is significantly lower than one audio signal is Even if it exists, the low-level sound is substantially inaudible due to the masking effect and the cocktail party effect. Therefore, even when two sounds are reproduced, it becomes easy to hear only the information by one sound signal. As described above, in the sound reproducing device of the present invention, the front direction of the first speaker mounting surface is the zero point direction of the second audio signal, so that only the information by the first audio signal can be easily heard in that direction. Further, in the sound reproducing device, the front direction of the second speaker mounting surface that is different in the direction of 90 degrees is the zero point direction of the first audio signal, so that only the information by the second audio signal can be easily heard in that direction. Therefore, two independent sounds can be spatially separated and reproduced in two directions different by 90 degrees compared to the case where two sounds are reproduced by a normal omnidirectional speaker system. .

  In the sound reproducing apparatus, it is particularly preferable that the first speaker and the second speaker be elongated electrodynamic speakers whose short-diameter length is shorter than the long-diameter length. The first speaker and the second speaker are arranged so that the major axis directions thereof are parallel to each other and the minor axis direction substantially coincides with each other, and the separation distance and the minor axis direction length of the first speaker and the second speaker substantially coincide with each other. If they are arranged so as to be close to each other, the distance between the speakers can be made narrower than that of a round normal speaker. When the substantial distance between the first speaker and the second speaker is shortened, the delay time in the delay means can be shortened, and unidirectional control can be performed up to a high frequency. Furthermore, a speaker including an elongated diaphragm has radiation directivity characteristics in which the directivity becomes narrower in the major axis direction, the directivity becomes wider in the minor axis direction, and approaches omnidirectionality. Therefore, since the width in the major axis direction can be increased in the direction of the zero point in the unidirectionality, there is an advantage that the range in which only information by one audio signal can be easily heard is widened.

  In addition, the directivity control unit relatively increases the level of the low-frequency region of the first signal or the second signal that is canceled due to the separation distance between the first speaker and the second speaker that are driven in substantially opposite phases. If the compensation means is further included, the bass component lost by the unidirectional control can be compensated. The balance of the reproduced sound can be improved by relatively emphasizing the bass component for canceling the bass component with the second speaker arranged close to the first speaker.

  In the sound reproduction device, the directivity control unit outputs the volume level of the output signal of the second filter circuit input to the first adder, or the volume level of the output signal of the first filter circuit input to the second adder. Can be switched between unidirectional and omnidirectional, by further including a level adjusting circuit that adjusts and outputs the radiated sound. If the volume level of the output signal of the first filter circuit or the second filter circuit is reduced, the unidirectionality approaches omnidirectionality. Therefore, two independent voices are reproduced spatially separated in two different directions of 90 degrees by unidirectional control, and two voices are mixed and radiated in all directions by omnidirectional control. Can be used separately.

  The sound reproducing device of the present invention includes a directivity control unit for controlling the directivity of a speaker. When reproducing two independent audio signals with a simple configuration, the sound reproducing device of the speaker that reproduces one audio signal is provided. At the front position, the reproduction level of the other audio signal is extremely low, and it is possible to easily listen to information by the one audio signal.

It is a figure explaining the sound reproduction apparatus 1 by preferable embodiment of this invention. Example 1 It is a figure explaining the speaker system 3 which comprises the sound reproduction apparatus 1 by preferable embodiment of this invention. Example 1 It is a figure explaining the elongate electrodynamic type speaker 20 which comprises the speaker system 3 of the sound reproduction apparatus 1 by preferable embodiment of this invention. (Example 2) It is a figure which illustrates notionally the unidirectional radiation characteristic and reproduction | regeneration sound field which are reproduced | regenerated with the sound reproduction apparatus 1 by preferable embodiment of this invention. Example 1 It is a graph explaining the directivity characteristic of the speaker system 3 which comprises the sound reproduction apparatus 1 by preferable embodiment of this invention. Example 1 It is a graph explaining the unidirectional radiation characteristic reproduced | regenerated with the sound reproduction apparatus 1 by preferable embodiment of this invention. Example 1

  Hereinafter, although the sound reproduction apparatus by preferable embodiment of this invention is demonstrated, this invention is not limited to these embodiment.

  FIG. 1 is a diagram illustrating a sound reproducing device 1 according to a preferred embodiment of the present invention. Specifically, FIG. 1 is a block diagram illustrating a configuration of the sound reproducing device 1. 2 is a diagram for explaining the speaker system 3 constituting the sound reproducing device 1. FIG. 2 (a) is a perspective view of the speaker system 3, and FIG. It is a top view explaining sp1 and sp2 which comprise. Further, FIG. 3 is a diagram for explaining an elongated electrodynamic speaker 20 as a specific example of sp1 and sp2 constituting the speaker system 3 of the sound reproducing device 1. FIG. 4 is a diagram for conceptually explaining the unidirectional radiation characteristic and the reproduced sound field reproduced by the sound reproducing device 1, and FIG. 4 (a) is a case where the audio signal a1 is reproduced. FIG. 4B shows a case where the audio signal a2 is reproduced. In addition, illustration and description of a part of the structure unnecessary for the description, an internal structure, and the like are omitted.

  The sound reproducing device 1 includes a directivity control circuit 2 and a speaker system 3. When reproducing the two independent audio signals a1 and a2, the sound reproducing device 1 can reproduce the sound so that the sound radiation characteristic varies depending on the direction and the sound reproduction level varies depending on the directivity control. In the case of the present embodiment, in the front direction d1 of the speaker sp1 that reproduces one audio signal a1, the reproduction level of the other audio signal a2 is extremely low, and one of the listeners (not shown) positioned in that direction It is possible to easily listen to information by the audio signal a1. Similarly, in the front direction d2 of the speaker sp2 that reproduces the other audio signal a2, the reproduction level of the one audio signal a1 is extremely low, and it is easy for listeners located in that direction to hear information from the other audio signal a2. it can.

  The directivity control circuit 2 includes a DSP (digital signal processor) 5 that receives and processes two audio signals a1 and a2, and a D / A converter that receives the output of three channels of the DSP 5 and converts it into an analog signal. 6 and an amplifier circuit 7 for amplifying and outputting these analog signals to the speaker system 3, respectively. The two audio signals a1 and a2 may be supplied to the DSP 5 as stereo signals (left signal L and right signal R). The directivity control circuit 2 has input terminals Input1 and Input2 for inputting the audio signals a1 and a2, and output terminals Output1 and Output2 for outputting the outputs of the two amplifier circuits 7. Specifically, the directivity control circuit 2 can be configured by a DSP that supports multi-channel audio and an AV receiver that incorporates a multi-channel amplifier circuit. Of course, the directivity control circuit 2 may be configured by another sound reproduction device including a DSP, a D / A converter, and an amplifier circuit.

  The speaker system 3 includes a vertically long and substantially rectangular parallelepiped cabinet 30 formed of resin or the like, and a wide foot portion 33 for preventing overturning on the bottom side thereof. The cabinet 30 includes a speaker mounting surface 31 and a speaker mounting surface 32 that is orthogonal to the speaker mounting surface 31 on one side surface thereof. The speaker sp1 is attached to the speaker attachment surface 31, and the speaker sp2 is attached to the speaker attachment surface 32. The speaker sp1 and the speaker sp2 of this embodiment are electrodynamic speakers having an elongated rectangular flat diaphragm, and the speaker mounting surface 31 and the speaker mounting are arranged so that the rectangular flat diaphragms are close to each other in the same orthogonal relationship. Attached to the surface 32. These two speakers preferably have substantially the same sound radiation characteristics, and the same is most preferable. It is preferable that the two speakers have the same positive and negative terminals for supplying signals to the magnetic circuit and the voice coil so that the audio signal is emitted in the same phase.

  As shown in FIG. 3, the electrodynamic speaker 20 used for the speakers sp <b> 1 and sp <b> 2 includes a thin rectangular planar diaphragm 25, an edge 26 that supports the periphery of the planar diaphragm 25 so as to vibrate, and a planar diaphragm. A plane for full-surface driving comprising a voice coil assembly 21 fixed to the back side of 25, a damper 24 that supports the voice coil assembly 21 so as to vibrate, a frame 27, and a plurality of magnetic circuits 28 including magnets. It is a thin speaker. The voice coil assembly 21 has three voice coils 23 connected in a lattice pattern by bobbins 22, and the speaker 20 includes three magnetic circuits 28 corresponding to the three voice coils 23. The thin rectangular speaker 20 has a length daL in the major axis direction da of about 12.5 cm and a length dbL in the minor axis direction db of about 4.8 cm.

  As illustrated, the speaker sp <b> 1 is attached so as to be closer to the speaker attachment surface 32 in the speaker attachment surface 31. The speaker sp2 is attached so as to be closer to the speaker attachment surface 31 in the speaker attachment surface 32. When viewed from the two speakers, the distance d between the center lines in the major axis direction is an isosceles triangle whose apex is the position of each center line and the corners formed by the speaker mounting surface 31 and the speaker mounting surface 32. Is equivalent to the length of two sides of equal length. In the case of the present embodiment, the separation distance d between the speakers is about 5 cm. That is, the separation distance d between the two speakers can be calculated from the distance between the center positions of the respective diaphragms.

  In the case of the present embodiment, since the elongated electrodynamic speaker 20 having a shorter short direction length dbL than the long direction length daL is used for the speaker sp1 and the speaker sp2, when the speaker sp1 and the speaker sp2 are arranged, the speaker If the sp1 and the speaker sp2 are arranged such that the major axis direction da thereof is parallel and the minor axis direction db is substantially coincident, the separation distance d (= 5.0 cm) between the speaker sp1 and the speaker sp2 is set. The length can be shortened to substantially the same length as the minor length direction dbL (= 4.8 cm). That is, if the frames 27 of the elongated electrodynamic speaker 20 are adjacent to each other in the minor axis direction so as not to interfere with each other, the speaker sp1 and the speaker sp2 can be separated to realize unidirectional acoustic radiation characteristics. Since the distance d can be shortened and these can be arranged close to each other, the distance between the speakers can be reduced as compared with a conventional round ordinary speaker.

  The cabinet 30 has a space for defining an acoustic capacity in the interior thereof in order to increase the vicinity of the lowest resonance frequency of each speaker and the following bass range. The interior of the cabinet 30 is preferably partitioned for each speaker so that sound waves radiated to the back side of the cone diaphragm do not interfere with each other. The cabinet 30 may employ various types of cabinets such as a sealed type, a bass reflex type, and a kelton type. The cabinet 3 of the speaker system 2 may be provided with a front grill (not shown), a punching net, or the like so as to protect the exposed speaker 10. Further, the speaker sp1 and the speaker sp2 may each be constituted by a speaker array in which a plurality of elongated electrodynamic speakers 20 are arranged so that the major axis directions thereof coincide with each other. When the speaker sp1 and the speaker sp2 are configured by a speaker array, a plurality of elongated electrodynamic speakers 20 may be connected in series and / or in parallel.

  The DSP 5 of the directivity control circuit 2 performs signal processing on the audio signals a1 and a2 which are digital signals, and outputs them. The DSP 5 includes a filter circuit 11a that filters the audio signal a1 input to the input terminal Input1, a filter circuit 11b that filters the audio signal a2 input to the input terminal Input2, and the phases of the audio signal a1 and the filter circuit 11b. An adder 12a for adding the inverted output; and an adder 12b for adding the audio signal a2 and the phase inverted output of the filter circuit 11a. The D / A converter 6 outputs the output signal of the adder 12a to the speaker sp1. And the output signal of the adder 12b is output to the speaker sp2 via the D / A converter 6 and the amplifier 7. Further, the DSP 5 includes level adjustment circuits 13a and 13b for adjusting the levels of the output signals of the filter circuit 11a and the filter circuit 11b, as will be described in other embodiments described later. Level adjustment circuits 13a and 13b may be multipliers that multiply values in the range of -1.0 to 1.0 so as to include the phase inversion in adders 12a and 12b instead. The DSP 5 also includes compensation filters 14a and 14b that relatively increase the levels of the low frequency regions of the audio signals a1 and a2, respectively, a delay circuit 15a that delays the audio signal a1 input to the adder 12a, and an adder 12b. And a delay circuit 15b for delaying the audio signal a2 input to.

  The two D / A converters 6 are respectively connected to the amplifier circuit 7, and each amplifier circuit 7 outputs the power-amplified signal to the output terminals Output 1 and Output 2. The two D / A converters 6 and the amplifier circuit 7 have substantially the same output characteristics. Thus, the directivity control circuit 2 is given a specific filter characteristic by relatively increasing the level of the low frequency region and the audio signal a1 delayed by relatively increasing the level of the low frequency region. The phase-inverted audio signal a2 is added and output to the output terminal Output1. Similarly, the audio signal a2 that is delayed by relatively increasing the level in the frequency domain and the level in the low frequency domain are relative to each other. And the audio signal a1 that has been given a specific filter characteristic and phase-inverted is added to the output signal Output2.

  FIG. 5 is a graph for explaining the directivity characteristic of the speaker system 3. Specifically, when the audio signal a1 is reproduced using only the speaker sp1 attached to the speaker attachment surface 31 of the speaker system 3, the sound pressure frequency characteristic (solid line) in the front direction d1 and the 90-degree direction It is the graph which overwrote the sound pressure frequency characteristic (dotted line) in d2. Since the speaker sp1 is a flat thin speaker that is driven on the entire surface and includes a thin rectangular flat diaphragm 25, the speaker sp1 is almost omnidirectional in a low frequency region up to about 400 Hz with a long wavelength, and in the front direction in a higher frequency region than that. It has a directivity characteristic that the level is lowered in the direction d2 by 90 degrees from d1.

  As a specific configuration of the cabinet unit 30 of the speaker system 3, the sound reproducing device 1 includes a speaker sp <b> 1, a speaker sp <b> 2, and a directivity control unit 2 that reflects the mounting conditions of the speaker mounting surface 31 and the speaker mounting surface 32. . That is, the filter circuit 11a and the filter circuit 11b of the DSP 5 of the directivity control circuit 2 have 90-degree direction directivity characteristics (FIG. 5: FIG. 5: d1) on the axial front direction sound pressure characteristics of the speakers sp1 and sp2. : Having a transfer function characteristic H (= d2 / d1) substantially the same as d2). The filter circuit 11a and the filter circuit 11b are preferably realized by an FIR filter (finite impulse response filter) having a tap number greater than or equal to a predetermined value. When deriving the transfer function characteristic H, the inverse characteristic may be calculated by giving a predetermined delay so as to satisfy the causality. In such a case, the delay circuit 15a and the delay circuit 15b The set delay time is preferably matched with the delay time of the transfer function characteristic H of the filter circuit 11a and the filter circuit 11b.

  As a result, as shown in the conceptual diagram of FIG. 4, the sound reproducing device 1 can realize good unidirectional radiation characteristics. That is, with respect to the audio signal a1, the speaker is based on the sound wave radiated from the speaker sp1 and the sound wave radiated from the speaker sp2 after being subjected to the transfer function characteristic H substantially the same as the 90-degree direction directivity and reversed in phase. A unidirectional acoustic radiation characteristic is realized in which the front direction d2 of the speaker mounting surface 32 to which sp2 is mounted is the zero point direction. Similarly, regarding the audio signal a2, the sound wave radiated from the speaker sp2 and the sound wave radiated from the speaker sp1 after being subjected to the transfer function characteristic H substantially the same as the 90-degree direction directivity and being phase-inverted, A unidirectional acoustic radiation characteristic is realized in which the front direction d1 of the speaker mounting surface 31 to which the speaker sp1 is mounted is the zero point direction.

  FIG. 6 is a graph for explaining unidirectional radiation characteristics reproduced by the sound reproducing device 1. Specifically, FIG. 6 shows the sound pressure frequency characteristic (solid line) in the front direction d1 of the speaker mounting surface 31 and the speaker mounting surface when unidirectional radiation characteristics are realized with respect to the audio signal a1. 31 is a graph in which the sound pressure frequency characteristic (dotted line) in the 90-degree direction d2 of 31 (also the front direction of the speaker mounting surface 32) is overwritten. The sound reproducing device 1 of the present embodiment realizes a good unidirectional radiation characteristic in which the level is reduced by about 15 to 20 dB over the entire audio band of about 200 Hz or more in the 90-degree direction d2 compared to the front direction d1. be able to. It should be noted that good unidirectional radiation characteristics can also be realized for the audio signal a2.

  Therefore, in the front direction d1 of the speaker mounting surface 31, the reproduction sound pressure level of the audio signal a1 is about 20 dB larger than the reproduction sound pressure level of the audio signal a2. Similarly, in the front direction d2 of the speaker mounting surface 32, the reproduction sound pressure level of the audio signal a2 is larger by about 20 dB than the reproduction sound pressure level of the audio signal a1. Thus, in the unidirectional zero point direction, the other audio signal is smaller than the other audio signal. If there is a reproduction level difference of about 20 dB, even if two sounds are reproduced, it becomes easy to listen only to information by one sound signal.

  The audio signals a1 and a2 input to the directivity control unit 2 are, for example, mutual audio signals a1 are female announcement voices, and the audio signal a2 is a male announcement voice having a different content from the audio signal a1. In the case of an independent audio signal that is uncorrelated to the audio signal, even if there is another audio signal that is significantly lower in playback level than the other audio signal, the low-level audio is substantially reduced due to the masking effect and cocktail party effect. I can't hear you. As described above, in the sound reproducing device 1, since the front direction d1 of the speaker mounting surface 31 is the zero point direction of the audio signal a2, only the information by the audio signal a1 can be easily heard in the direction d1. Further, in the sound reproducing device 1, since the front direction d2 of the speaker mounting surface 32 different in the direction of 90 degrees is the zero point direction of the audio signal a1, only the information by the audio signal a2 can be easily heard in the direction d2.

  In the DSP 5 of the directivity control circuit 2 according to the present embodiment, the input audio signals a1 and a2 are input to the compensation filters 14a and 14b, respectively, but the compensation filters 14a and 14b are connected to two output signals. Each can be replaced by one provided. The compensation filters 14a and 14b only need to relatively increase in advance the level of the low frequency region of the left signal L or the right signal R that is canceled due to the distance d between the speakers sp1 and sp2. The compensation filters 14a and 14b can enhance the balance of the sound image that is felt far away for the listener by relatively enhancing the bass component for which the bass component is canceled between two speakers arranged in close proximity. When the audio signals a1 and a2 are stereo audio signals including monaural components that are correlated with each other, the compensation filters 14a and 14b cancel the bass component between the speakers sp1 and the speakers sp2 that are arranged in proximity to each other. Compensation is also made for a reverse phase component (for example, (LR)) that becomes easy, so that a sense of spread of the stereo sound field can be maintained.

  When the substantial distance d between the speakers in the speaker system 3 can be shortened as in the sound reproducing device 1 of the present embodiment, the filter circuit 11a and the filter circuit 11b of the DSP 5 of the directivity control circuit 2 The filter can be shortened to enable unidirectional control up to a high frequency. When the separation distance d is about ½, the frequency band in which unidirectional control is possible (frequency at which dip occurs) can be doubled. In addition, the sound reproducing device 1 according to the present embodiment uses two electrodynamic speakers 20 including the planar diaphragm 25 and the voice coil assembly 21 in the speaker system 3. The voice coil assembly 21 of the electrodynamic speaker 20 has three voice coils 23 connected in a lattice pattern by bobbins 22 and can suppress the divided vibration on the flat diaphragm 25. The piston vibration regeneration range is extremely wide. As a result, unidirectional characteristics can be obtained better with a simpler configuration than in the prior art.

  In the sound reproducing apparatus 1 of the present embodiment, two independent audio signals in two directions d1 and d2 that are different from each other by 90 degrees compared to the case where two sounds are reproduced by a normal omnidirectional speaker system. a1 and a2 can be spatially separated and reproduced. When a normal omnidirectional speaker system is used, the speaker arrangement may be limited. However, in the sound reproduction device 1 according to the present embodiment, a listener positioned in the direction d1 by sound reproduction using directivity control, Different audio signals can be played back to different listeners located in different directions d2, and different audio contents can be provided.

  In order to change the unidirectionality in the sound reproduction apparatus 1 to non-directionality, the level adjustment circuits 13a and 13b of the directivity control circuit 2 may be adjusted so that the output becomes zero. If the outputs of the filter circuit 11a and the filter circuit 11b of the directivity control circuit 2 are not input to the adder 12b and the adder 12a, the audio signal a1 is reproduced non-directionally from the speaker sp1, and the audio signal a2 is reproduced from the speaker sp2. It is because it reproduces from non-directional. As described in the above embodiment, the level adjustment circuits 13a and 13b only need to adjust and output the relative levels of the outputs of the filter circuits 11a and 11b with respect to the audio signals a1 and a2.

  The sound reproducing device of the present invention is not only a stereo device that reproduces a stereo sound signal alone, or a multi-channel surround sound reproducing device, but also a speaker built in a video / audio device such as a display, or a speaker that reproduces sound. The present invention can also be applied to a game machine having a cabinet with a built-in and a game machine such as a slot machine. Further, the sound reproducing apparatus of the present invention can be applied to digital signage that reproduces content audio in one direction for reproducing audio and reproduces calling audio different from the content audio in the other direction.

DESCRIPTION OF SYMBOLS 1 Sound reproduction apparatus 2 Directivity control circuit 3 Speaker system 30 Cabinet 31, 32 Speaker mounting surface 32 Speaker mounting surface 33 Foot part 5 DSP
6 D / A converter 7 Amplifier circuit 11a, 11b Filter circuit 12a, 12b Adder 13a, 13b Level adjustment circuit 14a, 14b Compensation filter 15a, 15b Delay circuit 20 Speaker 21 Voice coil assembly 22 Bobbin 23 Voice coil 24 Damper 25 Planar diaphragm 26 Edge 27 Frame 28 Magnetic circuit sp1 Speaker sp2 Speaker

Claims (6)

A first speaker mounting surface; a cabinet portion including a second speaker mounting surface configured to be orthogonal to the first speaker mounting surface; a first speaker mounted on the first speaker mounting surface; and the second speaker. A second speaker having the same configuration as that of the first speaker attached to the attachment surface; and a directivity control unit that drives the first speaker and the second speaker to obtain a unidirectional radiation characteristic.
A first filter circuit for filtering the first audio signal; a second filter circuit for filtering the second audio signal; and a phase inverted output of the first audio signal and the second filter circuit. And a second adder that adds the second audio signal and the phase-inverted output of the first filter circuit, and outputs the output signal of the first adder to the first adder. And outputting the output signal of the second adder to the second speaker, and the first filter circuit and the second filter circuit are in front of the first speaker and the second speaker in the axial front direction. It has a transfer function characteristic that is substantially the same as a 90-degree directional characteristic based on sound pressure characteristics.
Sound playback device. The first speaker and the second speaker are elongated electrodynamic speakers having a shorter length in the shorter diameter direction than a length in the longer diameter direction, and the first speaker and the second speaker are respectively in the longer diameter direction. Are arranged so that the minor axis directions are substantially coincident with each other, and are arranged close to each other so that the separation distance between the first speaker and the second speaker and the length in the minor axis direction substantially coincide with each other.
The sound reproducing device according to claim 1. The first audio signal and the second audio signal input to the directivity control unit are independent audio signals that are uncorrelated with each other.
The sound reproducing device according to claim 1 or 2. The directivity control unit compensates for relatively increasing the level of the low frequency region of the first signal or the second signal that is canceled due to the separation distance between the first speaker and the second speaker. Further comprising means,
The sound reproducing device according to claim 2 or 3. The directivity control unit is configured to obtain a volume level of an output signal of the second filter circuit input to the first adder or a volume level of an output signal of the first filter circuit input to the second adder. It further includes a level adjustment circuit that adjusts and outputs each.
The sound reproducing device according to claim 1. The directivity control unit includes a first delay circuit that delays the first audio signal input to the first adder, and a second delay circuit that delays the second audio signal input to the second adder. And the set delay times of the first delay circuit and the second delay circuit are matched with the delay time of the transfer function characteristic,
The sound reproducing device according to claim 1.

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