JP2009177747A - Speech communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a speech communication device capable of preventing howling without decreasing a cancel amount for a speaker sound even when divided vibration of speaker diaphragm occurs. <P>SOLUTION: The speech communication device A includes the speaker SP outputting a sound from a front side of the diaphragm 23 to the outside, microphones M1 and M2 disposed opposite the front of the diaphragm 23 and picking up the sound to output sound signals, and a sound processing unit 10 which, after adjusting a gain and a delay time for the sound signals output by the microphones M1 and M2, removes the sound signal of the microphone M1 from the sound signal of the microphone M2 to transmit the resulting signal to the outside, wherein the microphone M2 picks up a voice that a speaker makes at sound pressure level equal to or higher than that of the microphone M1 and picks up the sound generated by the speaker SP at sound pressure level smaller than that of the microphone M1 to output a sound signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a call device.

  Conventionally, there is a communication device installed indoors with an interphone system or the like, which includes a speaker that outputs sound from a communication device installed in another place, a microphone that inputs sound transmitted to the other communication device, and the like. Yes. Since howling occurs when the sound generated from the speaker wraps around the microphone, various measures for preventing howling are taken.

  For example, as a first conventional example, a loop circuit including a speaker and a microphone is formed in a communication device, and howling occurs when the loop gain exceeds 1, so that loss in a variable loss circuit provided in the loop circuit occurs. Some control the amount so that the loop gain is 1 or less to prevent howling. Here, it is assumed that the smaller signal level of the transmission signal and the reception signal is not important, and the transmission loss of the variable loss circuit inserted in the transmission line having the smaller signal level is increased.

  However, in the first conventional example, when the distance between the microphone and the speaker is short, the level of the received voice that goes from the speaker to the microphone increases, the transmitted signal becomes larger than the received signal, and the voice comes out from the speaker. In spite of the reception state, the control circuit switches to the transmission state, and there is a state in which no sound to be output from the speaker is generated.

  Therefore, as a second conventional example, a pair of microphones, a delay circuit that delays the output of the microphone closer to the speaker by the delay time of the sound wave corresponding to the difference in distance between the two microphones and the speaker, both microphones and the speaker The level adjustment amplifier circuit that adjusts the level corresponding to the difference in distance between the two microphones to match the output level of both microphones with the sound from the speaker, and both microphone outputs that have passed through the delay circuit and level adjustment amplifier circuit There is a communication device that includes a differential amplifier circuit and uses the output of the differential amplifier circuit as a transmission signal.

In this communication device, after the sound from the speaker is picked up by a pair of microphones, the delay and level adjustment is performed so that the speaker sound input to both microphones is canceled by the differential amplifier circuit. Can be transmitted to prevent the howling, and further to transmit the transmitted voice without receiving blocking. (For example, refer to Patent Document 1).
Japanese Patent No. 2607257 (page 2, left column, line 13 to right column, third line, page 4, right column, lines 26 to 49, FIGS. 1 and 5)

  The entire diaphragm of a speaker normally vibrates with the same phase. However, when a sound wave to be radiated has a certain frequency, it generates a divided vibration in which a plurality of vibration regions having different phases are generated. As a form of the divided vibration, there are a division in the radial direction of the diaphragm and a concentric division, and the division number includes two divisions, four divisions, and the like.

  In the configuration in which the speaker sound input to both microphones is canceled by the differential amplifier circuit and the howling is prevented by canceling only the speaker sound as in Patent Document 1, the diaphragm is divided during the divided vibration. Since the phases and amplitudes of the sound waves radiated from the respective vibration regions are different from each other, it is difficult to cancel the speaker sound input to both microphones with the differential amplifier circuit, and the howling prevention effect is reduced.

  The present invention has been made in view of the above-described reasons, and an object of the present invention is to prevent howling without reducing the amount of cancellation of speaker sound even when the diaphragm of the speaker is divided and oscillated. It is to provide a communication device.

  According to the first aspect of the present invention, a speaker that is attached to the housing and outputs sound from one surface side of the diaphragm to the outside of the housing, and is disposed to face the one surface of the diaphragm, collects sound and outputs a sound signal. After adjusting the gain and delay time for the first and second microphones and the audio signals output from the first and second microphones, the audio signal of the first microphone is removed from the audio signal of the second microphone. The second microphone collects the sound emitted by the speaker at a sound pressure level lower than that of the first microphone, and the sound emitted by the speaker is equivalent to the first microphone. Sound is collected at the above sound pressure level and an audio signal is output.

  According to the present invention, the first and second microphones are both disposed to face one surface of the diaphragm, and the plurality of vibration regions of the diaphragm are substantially equidistant from each other with respect to the first and second microphones. Since the amplitude difference and phase difference generated in each sound signal emitted from each vibration region and collected by the first and second microphones are substantially the same value, the gain and delay time of the sound processing unit are adjusted. By doing so, the sound wave radiated from each vibration region can be canceled, and the howling prevention effect can be obtained even during divided vibration. That is, howling can be prevented without reducing the amount of cancellation of speaker sound even when the diaphragm of the speaker is split and vibrated.

  According to a second aspect of the present invention, in the first aspect, the sound collecting surface of the first microphone is provided to face one surface of the diaphragm, and the sound collecting surface of the second microphone is an audio output from the speaker. It is provided in the same direction as the direction.

  According to this invention, the second microphone collects the speaker sound at a sound pressure level lower than that of the first microphone, and collects the sound emitted by the speaker at a sound pressure level equal to or higher than that of the first microphone. Since the sound signal is output by sound, the speaker's sound signal can maintain a sufficient level while ensuring the amount of cancellation of the speaker sound by the sound processing unit.

  According to a third aspect of the present invention, in the first or second aspect, a front air chamber which is a space formed on one surface side of the speaker diaphragm is provided in the housing, and the first microphones are collected in the front air chamber. A sound surface is arranged.

  According to the present invention, since the sound emitted from the speaker is reflected inside the front air chamber and diverges outside the housing, the sound pressure level difference between the speaker sounds collected by the first and second microphones is further increased. The effect of maintaining a sufficient level of the speech signal of the speaker is improved while ensuring the amount of speaker sound cancellation by the processing unit.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the first and second microphones are juxtaposed along a vertical direction with respect to one surface of the diaphragm of the speaker. .

  According to the present invention, the howling prevention effect at the time of divided vibration is further improved.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, a rear air chamber that is a space formed on the other surface side of the diaphragm of the speaker is provided in the housing, and the rear air chamber is a space outside the housing. It is characterized by being electrically insulated.

  According to the present invention, since the rear air chamber is a space with a high degree of sealing, it is difficult for the reverse phase sound radiated from the back surface of the speaker to the rear air chamber to leak out of the rear air chamber, and the first and second microphones. However, it is possible to suppress the adverse effect on the howling prevention processing of the sound processing unit due to collecting the sound of opposite phase.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the first and second microphones are arranged on the same substrate on which a wiring pattern is formed.

  According to the present invention, the first and second microphones can be positioned efficiently.

  As described above, according to the present invention, there is an effect that howling can be prevented without reducing the amount of cancellation of speaker sound even when the diaphragm of the speaker is vibrating in a divided manner.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment)
The communication device A of the present embodiment is shown in FIGS. 1 to 3, and is configured by housing a call module MJ in a rectangular box-shaped device body A2 in which a call switch SW1 and a voice processing unit 10 are arranged. The apparatus main body A2 is formed, for example, by joining two resin molding members. After housing the call switch SW1, the voice processing unit 10, and the call module MJ, the joining members are joined by a fitting means or an adhesive. To do.

  The call module MJ includes a housing A1 having a width of 40 mm, a height of 30 mm, and a thickness of 8 mm. The housing A1 includes a body A10 having an opening on the rear surface and a flat cover A11 covering the opening of the body A10. , A speaker SP and a microphone substrate MB1. A later-described diaphragm 23 of the speaker SP is disposed so as to face a plurality of sound holes 12 drilled in the front surface of the housing A1 and a plurality of sound holes 60 drilled in the front surface of the apparatus main body A2.

  As shown in FIG. 3, the audio processing unit 10 is composed of an IC including a communication unit 10a, audio switch units 10b and 10c, an amplification unit 10d, and a signal processing unit 10e, and is arranged in the housing A1. A voice signal transmitted from the communication device A installed in another room or the like through the information line Ls is received by the communication unit 10a, amplified by the amplification unit 10d through the voice switch unit 10b, and then the speaker. Output from SP. Further, by operating the call switch SW1, a call can be made and each audio signal input from the microphone M1 (first microphone) and the microphone M2 (second microphone) on the microphone board MB1 is received by the signal processing unit 10e. After being subjected to signal processing to be described later, it passes through the voice switch unit 10c, and is transmitted from the communication unit 10a to the communication device A installed in another room or the like via the information line Ls. That is, it functions as an intercom that allows two-way calls between rooms. Note that the power of the communication device A may be supplied from an outlet provided in the vicinity of the installation location or may be supplied via the information line Ls.

  As shown in FIG. 1, the speaker SP is a cylindrical yoke 20 formed of an iron-based material having a thickness of about 0.8 mm such as cold rolled steel plate (SPCC, SPCEN), electromagnetic soft iron (SUY), etc., and having one end opened. The circular support body 21 is extended from the opening end of the yoke 20 toward the outside.

  A cylindrical permanent magnet 22 (for example, residual magnetic flux density of 1.39 T to 1.43 T) formed of neodymium is disposed in the cylinder of the yoke 20, and the outer peripheral edge of the dome-shaped diaphragm 23 is a support. 21 is fixed to the edge surface.

  The diaphragm 23 is formed of a thermoplastic plastic (for example, a thickness of 12 μm to 50 μm) such as PET (PolyEthyleneTerephthalate) or PEI (Polyetherimide). A cylindrical bobbin 24 is fixed to the rear surface of the diaphragm 23, and is formed by winding a polyurethane copper wire (for example, φ0.05 mm) around a paper tube of kraft paper at the rear end of the bobbin 24. A voice coil 25 is provided. The bobbin 24 and the voice coil 25 are provided so that the voice coil 25 is positioned at the opening end of the yoke 20, and freely move in the front-rear direction in the vicinity of the opening end of the yoke 20.

  A voice signal is input to the voice coil 25 via a pair of speaker wirings W. The speaker wiring W is made of resin at one end on the voice coil 25 side along the back surface of the circular diaphragm 23 in the radial direction. It is fixed and the other end is connected to the amplifying unit 10d of the audio processing unit 10.

  When an audio signal is input to the polyurethane copper wire of the voice coil 25, an electromagnetic force is generated in the voice coil 25 due to the current of the audio signal and the magnetic field of the permanent magnet 22, so that the bobbin 24 moves back and forth with the diaphragm 23. Visible in the direction. At this time, a sound corresponding to the audio signal is emitted from the diaphragm 23. That is, an electrodynamic speaker SP is configured.

  The outer peripheral end of the circular support 21 of the speaker SP is in contact with the inside of the front surface of the housing A1 facing the diaphragm 23, and the speaker SP is fixed with the diaphragm 23 facing the front surface of the housing A1 from the inside. Is done.

  When the speaker SP is fixed in the housing A1, the front air chamber Bf which is a space surrounded by the front inner side of the housing A1 and the front surface side (the diaphragm 23 side) of the speaker SP, the rear inner side and the inner side surface of the housing A1. A rear air chamber Br, which is a space surrounded by the speaker SP and the back surface side of the speaker SP (the yoke 20 side), is formed, and the front air chamber Bf passes through the sound hole 12 of the housing A1 and the sound hole 60 of the apparatus main body A2. It communicates with the outside. The rear air chamber Br becomes a space that is insulated (not communicated) with the front air chamber Bf because the end portion of the support 21 of the speaker SP and the inner surface of the housing A1 are in close contact with each other. Furthermore, when the body A10 of the housing A1 and the cover A11 are in close contact with each other, the rear air chamber Br becomes a space insulated from the outside air. That is, the rear air chamber Br is sealed and insulated from other spaces.

  The sound radiated from the back surface of the speaker SP (the back surface of the diaphragm 23) to the rear chamber Br is in phase with the sound radiated from the surface of the speaker SP (the surface of the diaphragm 23) to the front chamber Bf. (Hereinafter, the phase of the sound radiated from the front surface of the speaker SP is referred to as a positive phase, and the phase of the sound radiated from the rear surface of the speaker SP is referred to as an opposite phase). However, as described above, since the rear air chamber Br is a highly sealed space, the sound of the opposite phase radiated from the back surface of the speaker SP to the rear air chamber Br is difficult to leak out of the rear air chamber Br, and the rear air The reduction in the sound pressure due to the sound of the opposite phase leaking from the room Br wraps forward and cancels the sound of the normal phase radiated from the surface of the speaker SP, and the speaker SP is emitted to the speaker in front. Sound becomes easy to hear.

  Further, the other end side of the speaker wiring W is led out of the call module MJ through an insertion hole (not shown) drilled in the housing A1, and is connected to the audio processing unit 10 in the apparatus main body A2. After passing through the speaker wiring W, the insertion hole is closed with resin for sealing the rear air chamber Br.

  Next, as shown in FIG. 4, the microphone substrate MB1 includes a module substrate 2 having a rear surface 2a and a front surface 2b, and a pair of a microphone bare chip BC1 and ICKa1 is mounted on the rear surface 2a of the module substrate 2, A pair of the bare chip BC2 and ICKa2 is mounted on the front surface 2b of the module substrate 2, and between the bare chips BC1, ICKa1, and the wiring pattern (not shown) on the module substrate 2, and the wiring on the bare chip BC2, ICKa2, and the module substrate 2 After each pattern (not shown) is connected with wires W (wire bonding), the shield case SC1 is mounted on the rear surface 2a so as to cover the pair of bare chips BC1 and ICKa1, and the pair of bare chips BC2 and ICKa2 is covered. By mounting the shield case SC2 on the front surface 2b Bare BC1, ICKa1, constituted by the shield case SC1 microphones M1, bare chip BC2, ICKa2, and a composed microphone M2 with a shield case SC2.

  The microphone M1 is opposite to each other with the bottom surface side of the shield case SC1 provided with the sound hole F1 as a sound collecting surface, and the microphone M2 is opposite to the bottom surface side of the shield case SC2 provided with the sound hole F2. A sound collecting surface is provided on both sides of the module substrate 2 in the direction.

  As shown in FIG. 5, in the bare chip BC (bare chip BC1 or BC2), an Si thin film 1d is formed on one surface side of the silicon substrate 1b so as to close the hole 1c formed in the silicon substrate 1b. An electrode 1f is formed between them via an air gap 1e, and a pad 1g for outputting an audio signal is further provided to constitute a capacitor type silicon microphone. Then, an external acoustic signal vibrates the Si thin film 1d, whereby the capacitance between the Si thin film 1d and the electrode 1f changes to change the amount of charge, and the pad 1g changes with this change in the amount of charge. , 1g, a current corresponding to the acoustic signal flows. In this bare chip BC, the silicon substrate 1 b is die-bonded on the module substrate 2.

  FIG. 6A is a plan view of the microphone substrate MB1 as viewed from the rear surface 2a side of the module substrate 2. The module substrate 2 is formed in a rectangular shape, and includes a negative power supply pad P1, a positive power supply pad P2, and an output 1 pad. P3 and an output 2 pad P4 are provided along the edge of the module substrate 2.

  Then, as shown in FIG. 6B, the negative power supply pad P1 is connected to the negative side of the power supply voltage supplied from the outside, and the positive power supply pad P2 is connected to the positive side of the power supply voltage. Power is supplied to the microphones M1 and M2 through the pattern. Further, an audio signal collected by the microphone M1 is output from the output 1 pad P3 via a wiring pattern on the module substrate 2, and an audio signal collected by the microphone M2 is output from the output 2 pad P4. It is output via the upper wiring pattern. The ground of the audio signal output from the output pads P3 and P4 is shared by the negative power supply pad P1.

Thus, the power of the microphones M1 and M2 is supplied from the common negative power supply pad P1 and the positive power supply pad P2, and the ground of each output of the microphones M1 and M2 is shared by the negative power supply pad P1, so that the number of pads The configuration can be simplified. The microphone board MB1 can efficiently configure the signal lines and the power supply lines by transmitting signals and supplying power via the wiring patterns on the module board 2 as described above. Next, the operation of the microphone board MB1 will be described. To do.

  First, each current flowing from the bare chips BC1 and BC2 according to the collected acoustic signal is impedance-converted by ICKa1 and Ka2 and converted into a voltage signal, and output from the output 1 pad P3 and the output 2 pad P4 as audio signals, respectively. Is done.

  The ICKa (ICKa1 or Ka2) has the circuit configuration of FIG. 7, and is a constant IC composed of a chip IC that converts the power supply voltage + V (for example, 5V) supplied from the power supply pads P1 and P2 into a constant voltage Vr (for example, 12V). A voltage circuit Kb is provided, a constant voltage Vr is applied to the series circuit of the resistor R11 and the bare chip BC, and a connection midpoint between the resistor R11 and the bare chip BC is connected to the junction type J-FET element S11 via the capacitor C11. Connected to the gate terminal. The drain terminal of the J-FET element S11 is connected to the operating power supply + V, and the source terminal is connected to the negative side of the power supply voltage via the resistor R12. Here, the J-FET element S11 is for electrical impedance conversion, and the voltage at the source terminal of the J-FET element S11 is output as an audio signal. Note that the ICKa impedance conversion circuit is not limited to the above-described configuration, and may be, for example, a circuit having a function of a source follower circuit using an operational amplifier, or an audio signal amplification circuit in the ICKa if necessary. May be provided.

  In the present embodiment, the module substrate 2 is incorporated in the front wall of the housing A1, and the microphone M1 is inserted through the opening on the front surface of the housing A1 so that its sound collection surface is located in the front air chamber Bf, and on the bottom surface of the shield case SC1. The sound hole F1 of the perforated microphone M1 faces the center of the diaphragm 23 of the speaker SP, and the sound emitted by the speaker SP can be reliably collected through the sound hole F1.

  The microphone M2 is inserted through the opening on the front surface of the housing A1 so that the sound collection surface faces the outside of the housing A1, and the sound hole F2 of the microphone M2 formed on the bottom surface of the shield case SC2 is formed on the front surface of the apparatus main body A2. Since it faces the outside (front) of the housing A1 in the same direction as the output direction of the speaker SP so as to face the sound hole 61 provided, the communication device A is transmitted via the sound hole F2. The sound from the speaker located in front can be reliably collected.

  Further, since the microphones M1 and M2 are arranged by incorporating the module substrate 2 on which the microphones M1 and M2 are mounted in the housing A1, the microphones M1 and M2 can be positioned efficiently.

  When the distances from the center of the diaphragm 23 of the speaker SP to the sound holes F1 and F2 of the microphones M1 and M2 are X1 and X2, respectively, X1 <X2, and in this embodiment, the sound output of the speaker SP is the microphone. In order to prevent howling caused by picking up by M1 and M2, the following configuration is provided.

  First, as shown in FIG. 8, the signal processing unit 10e accommodated in the audio processing unit 10 includes an amplification circuit 30 that non-inverts and amplifies the output of the microphone M1, and an audio band (400 to 3000 Hz) from the output of the amplification circuit 30. ), A delay circuit 32 that delays the output of the bandpass filter 31, an amplifier circuit 33 that inverts and amplifies the output of the microphone M2, and an audio band from the output of the amplifier circuit 33. A band-pass filter 34 that removes noise of frequencies other than (400 to 3000 Hz), and an adder circuit 35 that adds outputs of the delay circuit 32 and the band-pass filter 34 are provided.

  9 to 12 show the sound signal waveforms of the respective parts of the signal processing unit 10 when the sound from the speakers is collected by the microphones M1 and M2, respectively. First, if the distances from the center of the diaphragm 23 of the speaker SP to the sound holes F1 and F2 of the microphones M1 and M2 are X1 and X2, respectively, X1 <X2. Therefore, when the sound from the speaker SP is picked up by the microphones M1 and M2, the output Y21 of the microphone M2 is more than the output Y11 of the microphone M1 depending on the distance between the speaker SP and the microphones M1 and M2 and the sensitivity of the microphones M1 and M2. The amplitude of the microphone M2 is small and the sound wave delay time [Td = (X2-X1) / Cv] (Cv is the speed of sound) corresponding to the difference (X2-X1) in the distance between the microphones M1 and M2 and the speaker SP. The phase of the output Y21 is delayed (see FIGS. 9A and 9B).

  The amplifier circuit 30 generates an output Y12 obtained by non-inverting amplification of the output Y11, and the amplifier circuit 33 generates an output Y22 obtained by inverting and amplifying the output Y21 and inverting the phase by 180 °. At this time, level adjustment corresponding to the difference (X2−X1) in the distance between the two microphones M1 and M2 and the speaker SP is performed to match the output levels of the two microphones M1 and M2 with respect to the sound from the speaker SP (FIG. 10 ( a) (b)). In the present embodiment, the amplification factor of the amplifier circuit 30 is less than 1, the amplification factor of the amplifier circuit 33 is approximately 1, and the amplifier circuit 33 may be omitted.

  Then, the band pass filters 31 and 34 generate outputs Y13 and Y23 obtained by removing noise of frequencies other than the audio band from the outputs Y12 and Y22 (see FIGS. 11A and 11B).

  Next, the delay circuit 32 is composed of a time delay element or a CR phase delay circuit, and delays the output of the microphone M1 closer to the speaker SP by the delay time Td, so that the output Y14 of the delay circuit 32 and The phase with the output Y23 of the bandpass filter 34 is matched to reduce noise on the transmitted audio signal.

  Then, the sound component from the speaker SP included in the output Y14 and the sound component from the speaker SP included in the output Y23 have the same amplitude and the same phase by the amplification process and the delay process. By adding Y23, an output Ya in which the audio signal corresponding to the audio from the speaker SP is canceled is generated (see FIGS. 12A to 12C). That is, in the output Ya, the sound component from the speaker SP is reduced.

  For the sound from the speaker SP, the amplitude of the output Y11 of the microphone M1 arranged with the sound collection surface facing the diaphragm 23 of the speaker SP is the microphone in which the sound collection surface is arranged toward the speaker H. On the other hand, the amplitude of the output Y21 of the microphone M2 is larger than the amplitude of the output Y11 of the microphone M1 with respect to the voice uttered by the speaker H in front of the microphones M1 and M2. Become. Furthermore, since the amplification factor of the amplification circuit 33 is larger than the amplification factor of the amplification circuit 30, the speech component from the speaker H included in the output Y23 is further larger than the speech component from the speaker H included in the output Y14. . That is, the amplitude difference between the speech component from the speaker H included in the output Y14 and the speech component from the speaker H included in the output Y23 becomes large, and even if the addition process is performed by the addition circuit 35, the output Ya Therefore, the signal corresponding to the voice uttered by the speaker H remains in a state where the amplitude is maintained sufficiently.

  As described above, the sound component from the speaker SP is reduced at the output Ya of the adder circuit 35, and the sound component emitted from the speaker H in front of the communication device A toward the microphone board MB1 remains, and at the output Ya The relative difference between the speech component from the speaker H to be retained and the speech component from the speaker SP to be reduced increases. That is, even when the sound from the speaker H and the sound from the speaker SP are generated at the same time, only the sound component from the speaker SP is reduced while maintaining a sufficient amplitude for the sound component from the speaker H. Therefore, howling that occurs when the microphones M1 and M2 pick up the sound output of the speaker SP can be prevented.

  When the signal processing unit 10e performs the speaker sound canceling process, the voice from the speaker H is also canceled at the same time. At this time, in order to set the amount of cancellation of the voice from the speaker H to 3 dB or less. Requires a sound pressure difference of 10 dB or more between the speaker sounds collected by the microphones M1 and M2 (see FIG. 13). And, in order to make the sound pressure difference 10 dB or more by the difference in distance between the microphones M1, M2 and the speaker SP (X2-X1), the diaphragm 23 of the speaker SP is considered as a point sound source. When the distance X1 from the center to the sound hole F1 of the microphone M1 is 1 mm, the distance X2 from the center of the diaphragm 23 to the sound hole F2 of the microphone M2 is required to be about 3.5 mm or more.

  In addition, since the microphone M1 reliably collects the sound emitted from the speaker SP, the howling prevention processing by the signal processing unit 10e can be reliably performed. Furthermore, since the sound collection surface of the microphone M2 and the diaphragm of the speaker SP are in the same direction, the acoustic coupling between the speaker SP and the microphone M2 is reduced, and the microphone M2 is difficult to collect the sound emitted by the speaker SP. .

  Furthermore, since the rear air chamber Br is a highly sealed space, the sound of the opposite phase radiated from the back surface of the speaker SP to the rear air chamber Br is difficult to leak out of the rear air chamber Br, and the microphones M1 and M2 are reversed. It is possible to suppress an adverse effect on the howling prevention processing of the signal processing unit 10e by collecting the sound of the phase.

  Next, the audio signal output from the signal processing unit 10e is output to the audio switch unit 10c, and the audio switch units 10b and 10c (see FIG. 3) further prevent howling by performing the following processing.

  First, the voice switch unit 10c takes in the output of the voice switch unit 10b as a reference signal, and performs an operation on the output of the signal processing unit 10e, thereby further processing the voice signal that has passed from the speaker SP to the microphones M1 and M2. Cancel. On the other hand, the voice switch unit 10b also captures the output of the voice switch unit 10c as a reference signal and performs an operation on the output of the communication unit 10a, thereby wrapping the voice signal from the speaker to the microphone at the other party on the other side. Cancel.

  Specifically, the audio switch units 10b and 10c are configured by a speaker SP-microphone M1, M2-signal processing unit 10e-audio switch unit 10c-communication unit 10a-audio switch unit 10b-amplifier unit 10d-speaker SP. By adjusting the amount of loss in a variable loss means (not shown) provided in the loop circuit, the loop gain is set to 1 or less to prevent howling. Here, it is assumed that the smaller signal level of the transmission signal and the reception signal is not important, and the transmission loss of the variable loss circuit inserted in the transmission line having the smaller signal level is increased.

  Here, if the radiated sound wave is lower than a certain frequency f1, the speaker SP performs a piston motion in which the entire surface of the diaphragm 23 vibrates with the same phase as shown in the amplitude velocity distribution of FIG. However, when the radiated sound wave has a frequency f1 or higher, a plurality of vibration regions having different phases generate split vibrations that occur in the diaphragm 23.

  FIG. 16 shows the sound pressure characteristics when the speaker SP is attached to a standard baffle defined in JIS C5532. In this embodiment, the range of the lowest resonance frequency fo is 500 to 600 Hz, and divided vibration occurs. The range of the lowest frequency f1 to be started is 800 to 900 Hz, and divided vibration is generated at a frequency higher than the frequency f1. If the standard baffle defined in the JIS C5532 is used, it is possible to measure the lowest resonance frequency equivalent to the case where the speaker SP is attached to a baffle plate having an infinite size (ideal baffle plate). Furthermore, it can be said that the lowest resonance frequency fo measured in this way is the same ideal characteristic as that of the speaker SP alone. In this embodiment, the standard baffle defined in JIS C5532 is used. However, even if the standard sealed box defined in JIS C5532 is used, a baffle plate having an infinite size (ideal baffle) is used. The lowest resonance frequency equivalent to the case where the speaker SP is attached to the plate) can be measured.

  Next, the influence of the piston motion and the divided vibration of the diaphragm 23 on the speaker sound canceling process will be described. In addition, as shown in FIGS. 15 (a) and 15 (b), the divided vibration includes two vibration regions G1 and G2 having opposite phases with respect to the phase inversion axis Za formed in the diameter direction of the diaphragm 23 as a boundary. A two-part vibration generated in the diaphragm 23 is illustrated.

  In FIGS. 17 and 18, the arrangement of the microphones M1 and M2 is different from that of the present invention, and the microphones M1 and M2 are arranged side by side on the speaker SP. However, the relationship between the distances X1 and X2 from the center of the diaphragm 23 of the speaker SP to the sound holes F1 and F2 of the microphones M1 and M2 is X1 <X2.

  First, the amplitude velocity distribution of FIG. 17 shows a case where the diaphragm 23 performs a piston motion in the vicinity of the lowest resonance frequency fo. The diaphragm 23 vibrates with the same phase and the same amplitude in all directions, and the sound wave radiated from the diaphragm 23 is considered to have no acoustic directionality in the positional relationship between the diaphragm 23 and the microphones M1 and M2. be able to. The sound wave radiated from the diaphragm 23 reaches the microphone M1, and then reaches the microphone M2 with a delay of the distance difference X10 (= X2−X1) between the two microphones M1 and M2. Therefore, the signal processing unit 10e sets the distance difference X10 (= X2-X1) between the microphones M1 and M2 in order to make the amplitude difference and phase difference between the speaker sounds collected by the microphones M1 and M2 zero. The gain and the delay time may be adjusted based on the above.

  Next, the amplitude velocity distribution in FIG. 18 shows a case where the diaphragm 23 vibrates in two near the frequency f1. The diaphragm 23 splits and oscillates in two vibration regions G1 and G2 with the phase inversion axis Za as a boundary, is displaced in the + direction in the vibration region G1, and is displaced in the-direction in the vibration region G2. An initial phase difference is generated between the sound waves radiated from the regions G1 and G2, and an acoustic directionality is generated between the vibration regions G1 and G2 and the microphones M1 and M2. In FIG. 18, the arrangement direction Zb of the microphones M1 and M2 is orthogonal to the phase inversion axis Za, and a distance difference X20 is generated in the vibration regions G1 and G2 with respect to the microphones M1 and M2, and the microphones M1 and M2 collect the distance. In the speaker sound to be struck, in addition to the above-described initial phase difference, an amplitude difference and a phase difference due to the distance difference X20 are generated.

  The amplitude difference and the phase difference generated in each sound signal emitted from the vibration area G1 and collected by the microphones M1 and M2, and each sound signal emitted from the vibration area G2 and collected by the microphones M1 and M2 The generated amplitude difference and phase difference are different from each other, and even if the gain and delay time of the signal processing unit 10e are adjusted, it is difficult to cancel both sound waves emitted from the vibration regions G1 and G2, Howling prevention effect is reduced.

  19 (a) to 19 (c) show the gain of the signal processing unit 10e and the gain of the signal processing unit 10e so that the cancellation amount of the speaker sound becomes substantially zero at 2 KHz during the piston movement shown in FIG. 17 and the two-part vibration shown in FIG. When the delay time is adjusted, the phase difference (FIG. 19A) and the amplitude difference (FIG. 19B) of the signals Y14 and -Y23 input to the adder circuit 35 and the signal Ya output from the adder circuit 35 are shown. The characteristics of the amount of cancellation of the speaker sound (FIG. 19C) are shown (Ya1 to Ya3 are characteristics during piston movement, and Yb1 to Yb3 are characteristics during two-part vibration). The frequency difference between the signals Y14 and -Y23 input to the adder circuit 35 and the amplitude difference (particularly in the vicinity of 3000 Hz to 4000 Hz) and the amount of cancellation of the speaker sound is wide when compared with the piston movement when the vibration is divided into two. It decreases over the band, which has an adverse effect on howling prevention.

  Therefore, in the present embodiment, the microphones M1 and M2 are arranged in parallel along the vertical direction (front-rear direction) with respect to the diaphragm 23 of the speaker SP so as to face the front surface of the diaphragm 23 of the speaker SP. As shown in the amplitude velocity distribution, the vibration regions G1 and G2 are substantially equidistant from each other with respect to the microphones M1 and M2, and the input signal Y14 of the adder circuit 35 generated due to the distance difference X20 between the vibration regions G1 and G2 -Y23 amplitude difference and phase difference are eliminated. Thus, the amplitude difference and phase difference generated in each sound signal emitted from the vibration region G1 and collected by the microphones M1 and M2, and each sound emitted from the vibration region G2 and collected by the microphones M1 and M2. The amplitude difference and the phase difference generated in the signal are substantially the same value, and by adjusting the gain and delay time of the signal processing unit 10e, both sound waves emitted from the vibration regions G1 and G2 can be canceled. It is possible to obtain a howling prevention effect even during divided vibration.

  The microphone M1 has a sound collection surface located in the front air chamber Bf, the sound hole F1 faces the center of the diaphragm 23 of the speaker SP, and the microphone M2 faces the sound collection surface outside the housing A1, The sound hole F2 faces the outside (front) of the housing A1 in the same direction as the output direction of the speaker SP. Since the sound emitted from the speaker SP is reflected in the front air chamber Bf and diverges outside the housing A1, the microphone M2 collects the speaker sound at a sound pressure level lower than the microphone M1 (for example, a sound of 10 dB or more). Pressure difference) and the voice uttered by the speaker is collected at a sound pressure level higher than that of the microphone M1, and a voice signal is output. Therefore, in the signal processing unit 10e, the relative difference between the speech component from the speaker H to be retained and the speech component from the speaker SP to be reduced becomes large, and the speaker is canceled while securing the amount of cancellation of the speaker sound. The audio signal can maintain a sufficient level.

  The arrangement of the microphones M1 and M2 is not limited to the configuration in which the microphones M1 and M2 are arranged in the front-rear direction so as to face the center of the diaphragm 23 of the speaker SP as described above. The microphone M2 is arranged facing the front, and the microphone M2 collects the sound emitted by the speaker at a sound pressure level equal to or higher than that of the microphone M1, and collects the sound of the speaker at a sound pressure level lower than the microphone M1. Any arrangement that outputs data may be used.

  For example, as shown in FIG. 21, the microphones M1 and M2 may be arranged in parallel in the direction (lateral direction) orthogonal to the front-rear direction on the front surface of the diaphragm 23. In this case, the microphone substrate MB2 is the module substrate 2 The microphones M1 and M2 are mounted on the rear surface 2a, and the rear surface 2a is disposed along the outer front surface of the housing A1. The microphone M1 is inserted through the opening on the front surface of the housing A1, the sound collection surface is located in the front air chamber Bf, and the sound hole F1 faces the center of the diaphragm 23 of the speaker SP. The microphone M2 is fitted into a recess provided in the front surface of the housing A1, and the sound hole F2 of the microphone M2 formed in the module substrate 2 is opposed to the sound hole 61 formed in the front surface of the apparatus main body A2. It faces the outside (front) of the housing A1 in the same direction as the output direction of the speaker SP. That is, with respect to the microphone M <b> 1 disposed to face the center of the diaphragm 23, the microphone M <b> 2 is disposed in a laterally biased manner on the front surface of the diaphragm 23.

  22 (a) to 22 (c), the gain and delay time of the signal processing unit 10e are adjusted so that the amount of cancellation of the speaker sound becomes substantially zero at 2 KHz during the two-part vibration of the communication device A of the present invention. At this time, the phase difference (FIG. 22A), the amplitude difference (FIG. 22B) of the signals Y14 and -Y23 input to the adder circuit 35, and the cancellation of the speaker sound in the signal Ya output from the adder circuit 35 Each characteristic of the quantity (FIG. 22C) is shown.

  When the radius of the diaphragm 23 of the speaker SP is 13 mm and the distance difference X10 between the microphones M1 and M2 in the radial direction is Y10 to Yc3 in FIGS. 22A to 22C, X10 = 0 mm (that is, 1 when using the microphone board MB1 shown in FIG. 1), Yd1 to Yd3 are X10 = 16 mm (that is, when the microphone M1 is not facing the diaphragm 23 in the communication device A of FIG. 21), and Ye3 is X10 = 8 mm. , Yf3 indicates each characteristic of X40 = 12 mm (that is, when the microphone M1 is opposed to the diaphragm 23 in the communication device A of FIG. 21). The smaller the distance difference X10, the smaller the phase difference and amplitude difference between the signals Y14 and -Y23 input to the adder circuit 35, and the frequency band in which the speaker sound cancellation amount in the signal Ya output from the adder circuit 35 is wide. Over the years.

  If the distance difference X10 is smaller than the radius of the diaphragm 23 (that is, the microphones M1 and M2 are disposed facing the front surface of the diaphragm 23), the amount of cancellation of speaker sound even during divided vibrations Therefore, the microphone M2 is disposed in the region D facing the front surface of the diaphragm 23 (see FIG. 21) with respect to the microphone M1 disposed facing the center of the diaphragm 23. If this is the case, it can be said that the vibration regions G1 and G2 are approximately equidistant from each other with respect to the microphones M1 and M2, and the input signals Y14 and -Y23 of the adder circuit 35 generated due to the distance difference X20 between the vibration regions G1 and G2. Thus, it can be said that a sufficient amount of cancellation of speaker sound by the signal processing unit 10e can be secured.

  Further, when the position of the microphone M1 is also moved in the region D and the positions of both microphones M1 and M2 are arbitrarily arranged in the region D facing the front surface of the diaphragm 23, the microphones M1 and M2 are both in the region. As long as it is disposed within D, the vibration regions G1 and G2 are approximately equidistant from each other with respect to the microphones M1 and M2, and are generated due to the distance difference X20 between the vibration regions G1 and G2 during the two-part vibration. It can be said that the amplitude difference and phase difference between the input signals Y14 and -Y23 of the adding circuit 35 to be eliminated can be eliminated.

  As the form of the divided vibration, in addition to the above-described divided vibration, four vibration regions G11 to G14 generated in the diaphragm 23 as shown in FIG. 23, or a plurality of concentric circles as shown in FIG. The vibration regions G21 and G22 include a circular divided vibration generated in the vibration plate 23, and the microphones M1 and M2 may both be disposed in the region D facing the front surface of the vibration plate 23 as in the case of the two-part vibration. For example, the plurality of vibration regions are substantially equidistant from each other with respect to the microphones M1 and M2, and the amplitude difference and phase difference generated in each sound signal emitted from each vibration region and collected by the microphones M1 and M2 are substantially the same value. By adjusting the gain and delay time of the signal processing unit 10e, it is possible to cancel the sound waves radiated from the plurality of vibration regions, and howl even in divided vibrations. It can be obtained preventing effect.

  The microphone M1 has a sound collection surface located in the front air chamber Bf, the sound hole F1 faces the diaphragm 23 of the speaker SP, and the microphone M2 has a sound collection surface facing the outside of the housing A1. If F2 is arranged so as to face the outside (front) of the housing A1 in the same direction as the output direction of the speaker SP, the sound emitted by the speaker SP is reflected inside the front air chamber Bf and diverges outside the housing A1. Therefore, the microphone M2 collects the speaker sound at a sound pressure level lower than the microphone M1 (for example, a sound pressure difference of 10 dB or more), and collects the sound emitted by the speaker at the sound pressure level higher than the microphone M1. Can be output. Therefore, it is possible to maintain a sufficient level of the speaker's voice signal while securing a cancellation amount of the speaker sound by the signal processing unit 10e.

  The relative positions of the microphones M1 and M2 are set such that X1 <X2 in the above embodiment, where the distances from the center of the diaphragm 23 of the speaker SP to the sound holes F1 and F2 of the microphones M1 and M2 are X1 and X2, respectively. However, even if X1 ≧ X2, the microphone M1 has its sound collection surface positioned in the front air chamber Bf as shown in FIG. 25, and the sound hole F1 is connected to the diaphragm 23 of the speaker SP. If the microphone M2 is disposed so that the sound collection surface faces the outside of the housing A1 and the sound hole F2 faces the outside (front) of the housing A1 in the same direction as the output direction of the speaker SP, Similarly, it is possible to maintain a sufficient level of the speaker's voice signal while securing a cancellation amount of the speaker sound by the signal processing unit 10e.

  Further, when both the microphones M1 and M2 are arranged with the sound collection surface facing the inside of the housing A1 and the sound holes F1 and F2 are both directed toward the center of the diaphragm 23 of the speaker SP, the microphone M1 as shown in FIG. Is arranged closer to the diaphragm 23 of the speaker SP than the microphone M2 (X1 <X2), the microphone M2 collects the speaker sound at a sound pressure level lower than the microphone M1 (for example, a sound pressure difference of 10 dB or more). In addition, it is possible to collect a voice uttered by the speaker at a sound pressure level higher than that of the microphone M1 and output a voice signal. Therefore, it is possible to maintain a sufficient level of the speaker's voice signal while securing a cancellation amount of the speaker sound by the signal processing unit 10e.

It is side surface sectional drawing which shows the structure of the communication apparatus of embodiment. (A) (b) It is a perspective view which shows the structure same as the above. It is a circuit diagram which shows the structure of an audio | voice processing part same as the above. It is side surface sectional drawing which shows the structure of a microphone substrate same as the above. It is side surface sectional drawing which shows the structure of a bare chip same as the above. It is the (a) simplified top view and (b) simplified circuit diagram which show the structure of a microphone substrate same as the above. It is a circuit diagram of an impedance conversion circuit same as the above. It is a circuit block diagram of a signal processing part same as the above. (A) (b) It is a signal waveform diagram of a signal processing part same as the above. (A) (b) It is a signal waveform diagram of a signal processing part same as the above. (A) (b) It is a signal waveform diagram of a signal processing part same as the above. (A)-(c) It is a signal waveform diagram of the signal processing part same as the above. It is a figure which shows the cancellation characteristic of a speaker sound same as the above. It is a perspective view which shows the motion of the diaphragm by piston movement same as the above. (A) (b) It is a perspective view which shows the motion of the diaphragm by the 2 divided vibration same as the above. It is a figure which shows the sound pressure characteristic of the speaker attached to the baffle board same as the above. It is a figure which shows propagation of the sound wave at the time of piston movement in the structure different from this invention. It is a figure which shows the propagation of the sound wave at the time of a division vibration in the structure different from this invention. (A)-(c) It is a figure which shows each characteristic at the time of piston movement same as the above, and a division vibration. It is a figure which shows propagation of the sound wave at the time of the division | segmentation vibration of embodiment. It is side surface sectional drawing which shows another structure of the communication apparatus of embodiment. (A)-(c) It is a figure which shows each characteristic at the time of the divided vibration same as the above. It is a perspective view which shows the motion of the diaphragm by 4 division vibration same as the above. It is a perspective view which shows the motion of the diaphragm by a circle division vibration same as the above. It is the schematic which shows another arrangement | positioning of a microphone same as the above. It is the schematic which shows another arrangement | positioning of a microphone same as the above.

Explanation of symbols

A Caller MJ Call module A1 Housing M1, M2 Microphone SP Speaker 23 Diaphragm 10 Sound processing unit

Claims (6)

A speaker attached to the housing and outputting sound from one side of the diaphragm to the outside of the housing;
First and second microphones arranged to face one surface of the diaphragm and collecting sound and outputting sound signals;
An audio processing unit that adjusts the gain and the delay time for the audio signals output from the first and second microphones, and then removes the audio signal of the first microphone from the audio signal of the second microphone and transmits it to the outside. And
The second microphone collects the sound emitted by the speaker at a sound pressure level lower than that of the first microphone, collects the sound emitted by the speaker at a sound pressure level equal to or higher than that of the first microphone, and obtains an audio signal. A communication device characterized by output.   The sound collecting surface of the first microphone is provided to face one surface of the diaphragm, and the sound collecting surface of the second microphone is provided in the same direction as the sound output direction from the speaker. The call device according to claim 1.   The front air chamber, which is a space formed on one surface side of the diaphragm of the speaker, is provided in the housing, and the sound collection surface of the first microphone is disposed in the front air chamber. 2. The communication device according to 2.   4. The communication device according to claim 1, wherein the first and second microphones are juxtaposed along a vertical direction with respect to one surface of the diaphragm of the speaker.   5. A rear air chamber, which is a space formed on the other surface side of the diaphragm of the speaker, is provided in the housing, and the rear air chamber is spatially insulated from the outside of the housing. Or a communication device according to claim 1.   6. The communication device according to claim 1, wherein the first and second microphones are arranged on the same substrate on which a wiring pattern is formed.

Images