JP2013073016A - Sound reproduction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sound reproduction device which includes a directivity control unit for controlling directivity of speakers and, when reproducing two independent sound signals, enables a user to easily hear information of one sound signal by extremely reducing a reproduction level of the other sound signal in a front position of a speaker reproducing one sound signal and properly controlling a mask signal.SOLUTION: In the sound reproduction device, a directivity control unit includes a first filter circuit, a second filter circuit, a first adder, a second adder, a masking circuit for outputting a mask signal, and a peripheral noise detection circuit for outputting peripheral noise characteristics to the masking circuit and performs such control that output levels and frequency spectra of a first mask signal and a second mask signal are changed in accordance with a sound volume level and a frequency spectrum of a peripheral noise signal outputted from the peripheral noise detection circuit.

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 becomes extremely low, the mask signal is appropriately controlled, 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).

  Further, conventionally, a speaker array in which a plurality of speaker units are arranged, and a plurality of audio signals are distributed to the plurality of speaker units, and sound emission timings of the respective audio signals emitted from these speaker units are emitted. A sound signal processing means for emitting sound beams having directivity in different directions from the speaker array, and a masking sound output means for outputting a masking sound signal for masking the plurality of sound signals, And the sound signal processing means distributes the masking sound signal output from the masking sound output means to the plurality of speaker units of the speaker array and emits the masking sound to be emitted from these speaker units. And at least the sound emitted from the speaker array Between over arm, a voice output device, characterized in that for sound masking sound (Patent Document 4). Conventionally, content audio output means for emitting sounds of a plurality of contents to a listening space corresponding to the listening position of each user, and contents of sounds to be emitted to other listening spaces for each content Masking sound output means for outputting a masking sound for masking, and masking sound setting information output means for receiving a masking sound emission setting and outputting masking sound setting information, wherein the masking sound output means comprises the masking sound output means. There is a content reproduction apparatus that performs settings for emitting the masking sound based on sound setting information (Patent Document 5).

  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.

  Further, in the prior art of Patent Document 4 or 5, when outputting a masking sound signal for masking the sound signal, there is a problem that it is difficult to appropriately control the masking sound signal. When ambient noise (background noise) is present in the reproduction sound field, the ambient noise exerts a masking effect, so that the masking sound signal level may be low. However, even if the masking sound signal is set by referring to the sound signal to be reproduced, the level of the masking sound signal is unnecessarily high unless the ambient noise is referred to, and even when two independent sound signals are reproduced. There is a problem that it becomes difficult to hear information by the 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) JP 2008-103851 A (FIGS. 1 to 7) JP 2010-266895 A (FIGS. 1 to 7)

  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 playing back two audio signals, the playback level of the other audio signal is extremely low at the front position of the speaker that reproduces one of the audio signals. An object of the present invention is to provide a sound reproducing device that can be easily heard.

  The sound reproducing device of the present invention includes a cabinet unit including a first speaker mounting unit and a second speaker mounting unit, a first speaker mounted on the first speaker mounting unit, a second speaker mounted on the second speaker mounting unit, A directivity control unit that drives one speaker and a second speaker to obtain unidirectional radiation characteristics, and a microphone that is connected to the directivity control unit, and the directivity control unit filters the first audio signal. A first filter circuit; a second filter circuit that filters the second audio signal; a first adder that adds the first audio signal and the phase-inverted output of the second filter circuit; a second audio signal; A second adder for adding the phase inversion output of the filter circuit; and a mask for inputting the first audio signal and the second audio signal and outputting the first mask signal and the second mask signal. An ambient noise detection circuit that generates an ambient noise signal from an input signal from the microphone and an output of the first adder and the second adder and outputs an ambient noise characteristic to the masking circuit. Controls to change the output level and frequency spectrum of the first mask signal and the second mask signal in accordance with the volume level and frequency spectrum of the ambient noise signal output by the ambient noise detection circuit. The second mask signal is added to the first audio signal or the second audio signal.

  Preferably, in the sound reproduction device of the present invention, the masking circuit of the directivity control unit includes a noise generation circuit, an analysis unit that analyzes the frequency characteristics of the first audio signal, the second audio signal, and the ambient noise signal, A mask filter unit that receives the output of the analysis unit and filters the output signal of the noise generation circuit, and the first mask signal and the second mask signal that are output signals of the mask filter unit are converted into the first audio signal or the second audio signal. A mask signal adding unit for adding, a third filter circuit and a fourth filter circuit in which the ambient noise detection circuit filters the outputs of the first adder and the second adder, respectively, and an input signal from the microphone A third adder that inverts and adds the output signal of the third filter circuit and the output signal of the fourth filter circuit and filtering the output of the third adder. It includes a fifth filter circuit for outputting to the analysis portion of the masking circuit.

  Preferably, in the sound reproduction device of the present invention, the directivity control unit controls the output levels of the first adder and the second adder according to the output level of the ambient noise signal of the ambient noise detection circuit. An output level adjustment circuit that outputs an output signal to the first speaker and the second speaker is further included. When the ambient noise signal increases, the output level adjustment circuit increases the output levels of the first adder and the second adder. And the masking circuit controls to reduce the output levels of the first mask signal and the second mask signal.

  Preferably, in the sound reproduction device of the present invention, the output level adjusting circuit of the directivity control unit includes a low-pass filter that outputs an effective value of the output of the third adder of the ambient noise detection circuit, and a low-pass filter. A multiplier whose coefficient is the output of the filter.

  Preferably, in the sound reproducing device of the present invention, the first filter circuit and the second filter circuit of the directivity control unit are in a predetermined direction with reference to the axial front direction sound pressure characteristics of the first speaker and the second speaker. And the third filter circuit and the fourth filter circuit of the ambient noise detection circuit are the responses from the first speaker and the second speaker to the microphone, which have substantially the same transfer characteristics (h1 / H1, h2 / H2) as The fifth filter circuit of the ambient noise detection circuit has a transfer characteristic (c1, c2) that is substantially the same as the characteristic, and the sum of the directivity characteristics (H1 + h1) of the first speaker and the second speaker in a predetermined direction is set to the first speaker and It has a transfer characteristic ((H1 + h1) / (c1 + c2)) divided by the sum of the response characteristics from the second speaker to the microphone (c1 + c2), and the masking circuit The mask filter unit analyzes from the product (S1 * (H2 + h2)) of the frequency characteristic output (S1) of the first audio signal of the analysis unit and the sum (H2 + h2) of the directivity characteristics in the predetermined direction of the first speaker and the second speaker. Transfer characteristic (S1 * (H2 + h2) -N1) obtained by subtracting the frequency characteristic output (N1) of the ambient noise signal of the unit, the frequency characteristic output (S2) of the second audio signal, and predetermined directions of the first speaker and the second speaker And the transfer characteristic (S2 * (H1 + h1) −N1) obtained by subtracting the frequency characteristic output (N1) of the ambient noise signal of the analysis unit from the product (S2 * (H1 + h1)) of the sum of the directivity characteristics (H1 + h1) .

  Preferably, in the sound reproducing device according to 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 second speakers are arranged so that the major axis directions thereof are parallel to each other and the minor axis directions are substantially coincident with each other, and the distance between the first speaker and the second speaker and the minor axis direction length are substantially coincident with each other. Has been placed.

  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 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 apparatus of the present invention includes a cabinet portion including a first speaker mounting surface and a second speaker mounting surface, a first speaker mounted on the first speaker mounting surface, and a second speaker mounted on the second speaker mounting surface. A directivity control unit that drives the first speaker and the second speaker to obtain unidirectional radiation characteristics, and a microphone that is connected to the directivity control unit, and when reproducing two independent audio signals, This is a sound reproducing apparatus in which the reproduction level of the other audio signal is extremely low at the front position of the speaker that reproduces one of the audio signals, and the mask signal is appropriately controlled to make it easier to listen to information from the one audio signal. 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. A first adder, a second adder that adds the second audio signal and the phase-inverted output of the first filter circuit, a masking circuit, and an ambient noise detection circuit.

  In the sound reproducing device of the present invention, for example, the first speaker mounting surface and the second speaker mounting surface of the cabinet section may be configured by two adjacent rectangular parallelepiped surfaces, and are arranged and configured in a mutually orthogonal positional relationship. Just do it. Since the sound reproducing device includes a directivity control unit that reflects the configuration of the speakers (first speaker, second speaker, first speaker mounting surface, and second speaker mounting surface) in the cabinet unit, good unidirectionality is achieved. 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. . The first filter circuit and the second filter circuit of the directivity control unit have transfer characteristics (h1 / H1) that are substantially the same as the directivity characteristics in a predetermined direction with reference to the on-axis front sound pressure characteristics of the first speaker and the second speaker. , H2 / H2), the unidirectionality as described above can be realized. 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 masking circuit of the directivity control unit inputs the first audio signal and the second audio signal, outputs the first mask signal and the second mask signal, and adds them to the first audio signal and the second audio signal. The ambient noise detection circuit generates an ambient noise signal from an input signal from the microphone and outputs from the first adder and the second adder, and outputs an ambient noise characteristic to the masking circuit. Then, the masking circuit of the directivity control unit changes the output level and frequency spectrum of the first mask signal and the second mask signal according to the volume level and frequency spectrum of the ambient noise signal output from the ambient noise detection circuit. To control. Therefore, it is possible to appropriately set the mask signal by referring to the first audio signal and the second audio signal to be reproduced and referring to the ambient noise. Since the ambient noise is referred to by the microphone, the level of the masking sound signal is not increased unnecessarily, and even when two independent sound signals are reproduced, information by one sound signal is obtained by directivity control and the masking effect. It is easy to hear only.

  Specifically, in the sound reproduction device, the masking circuit of the directivity control unit includes a noise generation circuit, an analysis unit that analyzes the frequency characteristics of the first audio signal, the second audio signal, and the ambient noise signal, A mask filter unit that receives the output and filters the output signal of the noise generation circuit, and a mask signal addition unit that adds the output signal of the mask filter unit to the first audio signal and the second audio signal. In addition, the ambient noise detection circuit includes a third filter circuit and a fourth filter circuit for filtering the outputs from the first adder and the second adder, respectively, an output signal of the third filter circuit from an input signal from the microphone, and A third adder that inverts and adds the output signals of the fourth filter circuit, and a fifth filter circuit that filters the output of the third adder and outputs the result to the analysis unit of the masking circuit. The third filter circuit and the fourth filter circuit of the ambient noise detection circuit have transfer characteristics (c1, c2) that are substantially the same as the response characteristics from the first speaker and the second speaker to the microphone. The five-filter circuit divides the sum of the directivity characteristics (H1 + h1) of the first speaker and the second speaker in a predetermined direction by the sum of the response characteristics from the first speaker and the second speaker to the microphone (c1 + c2) ((H1 + h1). ) / (C1 + c2)). In addition, the mask filter section of the masking circuit is a product (S1 * (H2 + h2)) of the frequency characteristic output (S1) of the first audio signal of the analysis section and the sum (H2 + h2) of the directivity characteristics in the predetermined direction of the second speaker. Transfer characteristic (S1 * (H2 + h2) −N1) obtained by subtracting the frequency characteristic output (N1) of the ambient noise signal from the analysis unit, the frequency characteristic output (S2) of the second audio signal, and the directivity of the first speaker in a predetermined direction. A transfer characteristic (S2 * (H1 + h1) −N1) obtained by subtracting the frequency characteristic output (N1) of the ambient noise signal of the analysis unit from the product (S2 * (H1 + h1)) of the characteristic sum (H1 + h1). preferable.

  Therefore, in addition to referring to the first audio signal and the second audio signal to be reproduced, referring to the level of the ambient noise and the frequency spectrum thereof, a mask signal that properly exhibits a masking effect in the presence of the ambient noise is obtained. Can be set. By using a broadband noise signal such as white noise generated by the noise generation circuit, it is possible to appropriately set the mask signal by referring to the ambient noise. Since the third filter circuit and the fourth filter circuit remove the reproduced sound of the first speaker and the second speaker from the input signal from the microphone, only the ambient noise can be detected. In addition, the microphone for detecting ambient noise is not necessarily installed at the listening point in the front direction of the first speaker or the second speaker and desired to exhibit the unidirectional control and the masking effect. Therefore, even when the microphone is installed at an arbitrary position close to the cabinet section, the ambient noise signal is passed through the fifth filter circuit, so that the influence of the ambient noise at the listening point is estimated and the masking circuit is appropriately masked. A filter can be set. As a result, the level of the masking audio signal does not increase unnecessarily, and even when two independent audio signals are reproduced, it is possible to easily hear only the information from one audio signal by directivity control and the masking effect. .

  In addition, the directivity control unit of the sound reproduction device controls the output levels of the first adder and the second adder according to the output level of the ambient noise signal of the ambient noise detection circuit, respectively, and controls the first speaker and the second speaker. An output level adjustment circuit that outputs an output signal may be further included. When the ambient noise signal becomes large, it becomes difficult to hear unless the audio signal is reproduced at a large level. Therefore, when the ambient noise signal increases, the output level adjustment circuit controls the output levels of the first adder and the second adder to be increased, and the masking circuit controls the first mask signal and the second mask signal. Control to reduce the output level. The output level adjustment circuit includes a low-pass filter that outputs an effective value of the output of the third adder of the ambient noise detection circuit, and a multiplier that uses the output of the low-pass filter as a coefficient. That's fine.

  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 separation distance between the first speaker and the second speaker is shortened, 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.

  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 the mask signal can be appropriately controlled to make it easier to listen to information from 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 DSP5 of the directivity control circuit 2 which comprises 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. FIG. 2 is a diagram for explaining the DSP 5 of the directivity control circuit 2 constituting the sound reproducing device 1. 3 is a diagram for explaining the speaker system 3 constituting the sound reproducing device 1, FIG. 3 (a) is a perspective view of the speaker system 3, and FIG. 3 (b) constitutes the speaker system 3. It is a top view explaining sp1 and sp2. Further, FIG. 4 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. 5 is a diagram for conceptually explaining the unidirectional radiation characteristic and the reproduced sound field reproduced by the sound reproducing device 1, and FIG. 5 (a) is a case where the audio signal a1 is reproduced. FIG. 5B 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, a speaker system 3, and a microphone Mic. 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 is 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 two 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. The microphone Mic is connected to the microphone input terminal MicInput of the directivity control circuit 2. An input signal from the microphone Mic is supplied to the DSP 5. 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. 4, 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 a speaker array is constituted by the speakers sp1 and sp2, 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; an adder 12b for adding the audio signal a2 and the phase inverted output of the filter circuit 11a; a masking circuit 14; an ambient noise detecting circuit 15 connected to the microphone input terminal MicInput; And an output level adjusting circuit 16 for outputting the output signal of the adder 12a to the speaker sp1 via the D / A converter 6 and the amplifier 7, and the output signal of the adder 12b to the speaker sp2 of the D / A converter. 6 and the amplifier 7 for output. 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 further includes a delay circuit 17a that delays an audio signal input to the adder 12a and a delay circuit 17b that delays an audio signal input to the adder 12b.

  The masking circuit 14 of the DSP 5 adds the first mask signal m1 or the second mask signal m2 to the input audio signals a1 and a2, and outputs the result to the filter circuit 11a and the filter circuit 11b. The ambient noise detection circuit 15 of the DSP 5 generates an ambient noise signal n1 from the input signal from the microphone Mic and the outputs of the first adder 12a and the second adder 12b, and outputs the ambient noise signal n1 to the masking circuit 14 and the output level. To the adjustment circuit 16. The output level adjustment circuit 16 controls the output levels of the first adder 12a and the second adder 12b in accordance with the output level of the ambient noise signal n1 of the ambient noise detection circuit 15, respectively, and controls two D / A converters. 6 outputs an output signal.

  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. In this way, the directivity control circuit 2 adds the audio signal a1 delayed by the addition of the mask signal and the audio signal a2 that has been subjected to phase inversion by adding the mask signal to give a specific filter characteristic. Similarly, the audio signal a2 added with the mask signal and delayed by the addition of the mask signal and the audio signal a1 with the mask signal added to give a specific filter characteristic and inverted in phase are similarly added to the output terminal Output1. And output to the output terminal Output2.

  FIG. 6 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.

  H1, h1, H2, h2, c1, and c2 in FIG. 1 indicate transfer functions from the speaker system 3 to respective listening positions and directions. 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. . In other words, the filter circuit 11a of the DSP 5 of the directivity control circuit 2 has the 90-degree direction directivity characteristic of the speaker sp2 with reference to the axial front direction sound pressure characteristic (FIG. 1: H1 and FIG. 6: d1) of the speaker sp1 (see FIG. 1: h1 and FIG. 6: d2) have substantially the same transfer function characteristics (= h1 / H1). On the other hand, the filter circuit 11b has a 90-degree direction directivity characteristic (FIG. 1: h2 and FIG. 6: d2) of the speaker sp1 with reference to the axial front direction sound pressure characteristic (FIG. 1: H2 and FIG. 6: d1) of the speaker sp2. ) And transfer function characteristics (= h2 / H2). 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 the transfer function characteristic is derived, the inverse characteristic may be calculated by giving a predetermined delay so as to satisfy the causality. In such a case, the delay circuit 17a and the delay circuit 17b are set to the respective settings. The delay time is preferably matched with the delay time of the transfer function characteristics of the filter circuit 11a and the filter circuit 11b.

  As a result, as shown in the conceptual diagram of FIG. 5, the sound reproducing device 1 can realize good unidirectional radiation characteristics. That is, regarding the audio signal a1, the speaker sp2 is generated by the sound wave radiated from the speaker sp1 and the sound wave radiated from the speaker sp2 after being phase-inverted and subjected to a transfer function characteristic substantially the same as the 90-degree direction directivity. A unidirectional acoustic radiation characteristic is realized in which the front direction d2 of the speaker mounting surface 32 to which is mounted is the zero point direction. Similarly, with respect to 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 a transfer function characteristic substantially the same as the 90-degree direction directivity and radiated from the speaker sp1 A unidirectional acoustic radiation characteristic is realized in which the front direction d1 of the speaker mounting surface 31 to which sp1 is mounted is the zero point direction.

  FIG. 7 is a graph for explaining unidirectional radiation characteristics reproduced by the sound reproducing device 1. Specifically, FIG. 7 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.

  Since the DSP 5 of the directivity control unit 2 includes the masking circuit 14 in the sound reproduction device 1, it is possible to generate a masking sound that is appropriately controlled in consideration of ambient noise and make it easy to hear only one audio signal. . FIG. 2 is a diagram illustrating the DSP 5 of the directivity control unit 2. The masking circuit 14 of the DSP 5 of the directivity control unit 2 adds a first mask signal m1 to be added to the audio signal a1 and the audio signal a2 according to the volume level and frequency spectrum of the ambient noise signal n1 output from the ambient noise detection circuit 15. Control is performed to change the output level and frequency spectrum of the second mask signal m2. Therefore, the mask signal can be appropriately set by referring to the audio signal a1 and the audio signal a2 to be reproduced and referring to the ambient noise.

  The masking circuit 14 of the DSP 5 includes a noise generation circuit 40 that generates white noise, an analysis filter 41a that analyzes the frequency characteristics of the audio signal a1, an analysis filter 41b that analyzes the frequency characteristics of the audio signal a2, and an ambient noise detection circuit. 15, an analysis filter 44 for analyzing the frequency characteristics of the output signal, mask filters 42a and 42b for receiving the output of these analysis filters constituting the analysis unit and filtering the output signal of the noise generation circuit 40, and a mask filter 42a And mask signal adders 43a and 43b for adding the output signals (first mask signal m1 and second mask signal m2) of 42b to the audio signal a1 or the audio signal a2. The output of the mask signal adder 43a is input to the filter circuit 11a and the delay circuit 17a. The output of the mask signal adder 43b is input to the filter circuit 11b and the delay circuit 17b. The noise signal generated by the noise generation circuit 40 may be colored noise such as pink noise and brown noise having frequency characteristics, in addition to white noise (white noise) having the same level at all frequencies.

  The ambient noise detection circuit 15 generates an ambient noise signal n1 from the input signal from the microphone Mic and the output signal to the D / A converter 6 and outputs the ambient noise signal n1 to the analysis filter 44 of the masking circuit 14. The ambient noise detection circuit 15 includes a third filter circuit 51 and a fourth filter circuit 52 that respectively filter the outputs of the first adder 12a and the second adder 12b that have been level-adjusted by the output level adjustment circuit 16, and a microphone Mic. Adders 53 and 54 for inverting the phase of the output signal of the third filter circuit 51 and the output signal of the fourth filter circuit 52 from the input signal from the input signal, and adding the output of the adder 54 to the masking circuit 14 And a fifth filter circuit 55 for input to the analysis unit.

  The output level adjustment circuit 16 includes a low-pass filter 60 that outputs an effective value of the output of the adder 53 of the ambient noise detection circuit 15, and multipliers 61a and 61b that use the output of the low-pass filter 60 as a coefficient. ,including. The multipliers 61a and 61b control the output levels of the first adder 12a and the second adder 12b in accordance with the output level of the ambient noise signal n1 detected by the ambient noise detection circuit 15, respectively. 2 Outputs an output signal to the speaker sp2.

  The third filter circuit 51 and the fourth filter circuit 52 of the ambient noise detection circuit 15 have transfer characteristics (c1, c2) that are substantially the same as the response characteristics from the first speaker sp1 and the second speaker sp2 to the microphone Mic. Accordingly, the output signal of the adder 53 is a signal substantially equivalent to the sound wave radiated from the first speaker sp1 and the second speaker sp2 and reaching the microphone Mic. Since the sound wave of the ambient noise and the sound wave emitted from the first speaker sp1 and the second speaker sp2 reach the microphone Mic, the adder 54 cancels the sound emitted from the first speaker sp1 and the second speaker sp2. Thus, only ambient noise can be detected as the ambient noise signal n1.

  In addition, the fifth filter circuit 55 of the ambient noise detection circuit 15 includes an axial front direction sound pressure characteristic (FIG. 1: H1 and FIG. 6: d1) of the speaker sp1 and a 90-degree direction directivity characteristic (FIG. 1: h1) of the speaker sp2. And FIG. 6: a transfer characteristic ((H1 + h1) / (c1 + c2)) obtained by dividing the sum (H1 + h1) with d2) by the sum (c1 + c2) of response characteristics from the first speaker sp1 and the second speaker sp2 to the microphone Mic. . The fifth filter circuit 55 filters the ambient noise signal n1 output from the adder 54 and inputs the filtered signal to the analysis filter 44 of the masking circuit 14. The microphone Mic for detecting the ambient noise is not always located at the listening point in the front direction of the first speaker sp1 or the second speaker sp2 and desired to exhibit the unidirectional control and the masking effect. Even when the signal is installed at an arbitrary position close to the cabinet section 30, the ambient noise signal is passed through the fifth filter circuit 55 to estimate the influence of the ambient noise at the listening point and appropriately mask the masking circuit 14. Filters 42a and 42b are set.

  Therefore, the analysis filter 44 of the masking circuit 14 analyzes the frequency characteristic of the ambient noise signal n1 and transmits the frequency characteristic output (N1) of the ambient noise signal n1 to the mask filters 42a and 42b of the masking circuit 14. Similarly, the analysis filter 41a of the masking circuit 14 analyzes the frequency characteristic of the audio signal a1 and transmits the frequency characteristic output (S1) to the mask filter 42a of the masking circuit 14, and the analysis filter 41b The frequency characteristic of the signal a2 is analyzed, and the frequency characteristic output (S2) is transmitted to the mask filter 42b of the masking circuit 14. The mask filter 42a of the masking circuit 14 of the DSP 5 is a product (S1) of the frequency characteristic output S1 of the first audio signal a1 and the sum (H2 + h2) of the directivity characteristics of the front of the second speaker sp2 and the 90 ° direction of the first speaker sp1. * (H2 + h2)) is set to have a transfer characteristic (S1 * (H2 + h2) −N1) obtained by subtracting the frequency characteristic output (N1) of the ambient noise signal n1 analyzed by the analysis filter 44. The mask filter 42b of the masking circuit 14 is a product (S2 * () of the frequency characteristic output S2 of the audio signal a2 and the sum (H1 + h1) of the directivity characteristics of the front of the first speaker sp1 and the 90 ° direction of the second speaker sp1. H1 + h1)) is set to have a transfer characteristic (S2 * (H1 + h1) −N1) obtained by subtracting the frequency characteristic output (N1) of the ambient noise signal n1 analyzed by the analysis filter 44.

  The noise generation circuit 40 of the masking circuit 14 generates white noise and inputs it to the mask filters 42a and 42b, and outputs a first mask signal m1 and a second mask signal m2, respectively. The mask signal adder 43a adds the second mask signal m2 to the audio signal a1 and outputs it, and the mask signal adder 4b adds the first mask signal m1 to the audio signal a2 and outputs it. That is, the level of the mask signal is set to be the minimum level effective for masking and lower than the reproduction level of the audio signal to be reproduced in the listening direction. Therefore, it is possible to set the first mask signal m1 and the second mask signal m2 that appropriately exhibit the masking effect in the presence of the ambient noise with reference to the ambient noise level and its frequency spectrum. Since the mask filters 42a and 42b relatively reduce the level of the frequency band in which the audio signal a1 and the audio signal a2 and the ambient noise of the white noise exist, depending on the audio signal a1, the audio signal a2, and the ambient noise. The first mask signal m1 and the second mask signal m2 that do not overlap can be generated. Since the ambient noise is referred to by the microphone Mic, the levels of the first mask signal m1 and the second mask signal m2 are not unnecessarily increased, and directivity control and masking can be performed even when two independent audio signals are reproduced. Due to the effect, it is possible to easily listen only to information by one audio signal.

  The directivity control unit 2 of the sound reproducing device 1 controls the output levels of the first adder 12a and the second adder 12b in accordance with the output level of the ambient noise signal n1 of the ambient noise detection circuit 15, respectively. Since the output level adjustment circuit 16 that outputs output signals to the first speaker sp1 and the second speaker sp2 is included, if the ambient noise signal n1 becomes large and difficult to hear due to the masking effect, the audio signal a1 and the audio signal a2 are increased. It can be played at levels to make it easier to listen. The output level adjustment circuit 16 includes a low-pass filter 60 that outputs an effective value of the output of the third adder of the ambient noise detection circuit, and multipliers 61a and 61b that use the output of the low-pass filter 60 as a coefficient. Therefore, when the level of the ambient noise signal n1 increases, the output level of the first adder 12a and the second adder 12b is controlled to increase, and the masking circuit 14 controls the first mask signal m1 and the second mask. Control is performed to reduce the output level of the signal m2.

  In the DSP 5 of the directivity control circuit 2 of the present embodiment, the input audio signal a1 and audio signal a2 may be input to a compensation filter (not shown). The compensation filter may be any filter that relatively increases in advance the levels of the low-frequency region of the audio signal a1 and the audio signal a2 that are canceled due to the distance d between the speakers sp1 and sp2. The compensation filter can enhance the balance of the sound image that is felt far away by the listener by relatively enhancing the low-frequency component in which the low-frequency component is canceled between two speakers arranged in close proximity. When the audio signal a1 and the audio signal a2 are stereo audio signals including monaural components that are correlated with each other, the compensation filter easily cancels the low-frequency component between the speakers sp1 and the speakers sp2 that are arranged in close proximity. As a result, the sense of spreading 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. Of course, the speakers sp1 and sp2 used in the speaker system 3 may be electrodynamic speakers including a cone-shaped diaphragm having a round outer shape.

  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 and masking sounds can be played back to different listeners located in different directions d2 to provide different audio contents.

  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 14 Masking circuit 15 Ambient noise detection circuit 16 Output level adjustment circuit 17a, 17b 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 mic Microphone

Claims (8)

A cabinet portion including a first speaker attachment portion and a second speaker attachment portion, a first speaker attached to the first speaker attachment portion, a second speaker attached to the second speaker attachment portion, the first speaker, and the first speaker A directivity control unit that drives two speakers to obtain a unidirectional radiation characteristic, and a microphone connected to the directivity control unit,
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. A first adder for adding the second audio signal, a second adder for adding the phase inverted output of the first filter circuit, and the first audio signal and the second audio signal. An ambient noise signal is generated by generating an ambient noise signal from a masking circuit for outputting a first mask signal and a second mask signal, an input signal from the microphone, and an output from the first adder and the second adder. An ambient noise detection circuit that outputs to the masking circuit,
The masking circuit is controlled to change the output level and frequency spectrum of the first mask signal and the second mask signal according to the volume level and frequency spectrum of the ambient noise signal output from the ambient noise detection circuit. And adding the first mask signal and the second mask signal to the first audio signal or the second audio signal,
Sound playback device. The masking circuit of the directivity control unit receives a noise generation circuit, an analysis unit that analyzes frequency characteristics of the first audio signal, the second audio signal, and the ambient noise signal, and an output of the analysis unit A mask filter unit that filters the output signal of the noise generation circuit, and the first mask signal and the second mask signal that are output signals of the mask filter unit are added to the first audio signal or the second audio signal A third filter circuit and a fourth filter circuit for filtering the outputs from the first adder and the second adder, respectively, and A third adder that inverts and adds the output signal of the third filter circuit and the output signal of the fourth filter circuit from the input signal, and the output of the third adder It includes a fifth filter circuit to be output to the analysis unit of the masking circuit to filter and,
The sound reproducing device according to claim 1. The directivity control unit controls the output levels of the first adder and the second adder according to the output level of the ambient noise signal of the ambient noise detection circuit, respectively, and controls the first speaker and the second speaker. An output level adjustment circuit for outputting an output signal to the speaker;
When the ambient noise signal increases, the output level adjustment circuit controls the output levels of the first adder and the second adder to be increased, and the masking circuit includes the first mask signal and the second adder. Control to reduce the output level of the second mask signal;
The sound reproducing device according to claim 1 or 2. The output level adjustment circuit of the directivity control unit includes a low-pass filter that outputs an effective value of the output of the third adder of the ambient noise detection circuit, and a multiplication that uses the output of the low-pass filter as a coefficient. Including,
The sound reproducing device according to claim 3. The first filter circuit and the second filter circuit of the directivity control unit transmit substantially the same directivity characteristics in a predetermined direction with reference to the axial frontal sound pressure characteristics of the first speaker and the second speaker. Characteristics (h1 / H1, h2 / H2), and the third filter circuit and the fourth filter circuit of the ambient noise detection circuit have response characteristics from the first speaker and the second speaker to the microphone. The fifth filter circuit of the ambient noise detection circuit has substantially the same transfer characteristics (c1, c2), and the sum (H1 + h1) of the directivity characteristics in a predetermined direction of the first speaker and the second speaker is A transfer characteristic ((H1 + h1) / (c1 + c2)) divided by the sum of response characteristics from one speaker and the second speaker to the microphone (c1 + c2); The mask filter section of the masking circuit is a product of the frequency characteristic output (S1) of the first audio signal of the analysis section and the sum (H2 + h2) of the directivity characteristics of the first speaker and the second speaker in a predetermined direction. The transfer characteristic (S1 * (H2 + h2) −N1) obtained by subtracting the frequency characteristic output (N1) of the ambient noise signal of the analysis unit from the (S1 * (H2 + h2)), and the frequency characteristic output (S2) of the second audio signal ) And the sum (H1 + h1) of directivity characteristics in a predetermined direction of the first speaker and the second speaker (S2 * (H1 + h1)), the frequency characteristic output (N1) of the ambient noise signal of the analysis unit is subtracted Transfer characteristics (S2 * (H1 + h1) −N1),
The sound reproducing device according to claim 1. 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 any one of claims 1 to 6. 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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