JP4966098B2 - Telephone device - Google Patents

Description

  The present invention relates to a call device used for an interphone or the like.

  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 has been proposed a communication device that includes a differential amplifier circuit as described above and uses the output of the differential amplifier circuit as a transmission signal.

In this communication device, after picking up the sound from the speaker with a pair of microphones, the delay and level adjustment is performed so that the sound component from the speaker input to both microphones is canceled by the differential amplifier circuit. The transmitted voice can be transmitted in a state in which only the voice component from the speaker is removed and no reception blocking occurs. (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)

  In a conventional communication device, an electret condenser microphone Mp as shown in FIG. 17 is used as a microphone. In the electret condenser microphone Mp, a ring 101 disposed on a printed board 100 supports an electrode 102 made of a metal plate, and a brass ring 103 is provided between the electrode 102 and the printed board 100. Further, a diaphragm 104 is disposed opposite to the electrode 102, and the diaphragm 104 is supported by a brass ring 105. A spacer 106 is disposed in an air gap of about 30 μm formed between the electrode 102 and the diaphragm 104. Then, the case 107 on the printed circuit board 100 covers the above-described parts, thereby forming the outer shell of the electret condenser microphone Mp.

  In the electret condenser microphone Mp having the above-described configuration, the diaphragm 104 is disposed in parallel in the vicinity of the electrode 102. It is composed of a polymer film such as polycarbonate or Teflon in which electric charges are confined (that is, in a charged state). Since the external acoustic signal vibrates the diaphragm 104, the distance between the diaphragm 104 and the electrode 102 fluctuates, so the charging state of the electrode 102 changes, and the acoustic signal varies with the amount of electricity. Can be taken out as. Note that electric charge is injected into the diaphragm 104 by corona discharge or the like.

  However, since the electret condenser microphone Mp needs to charge the diaphragm 104, the sensitivity is deteriorated due to a decrease in the charge amount of the diaphragm 104 due to heat, aging, etc., or a fluctuation in the charge amount of the diaphragm 104 due to vibration. End up. Therefore, in the configuration in which the speaker sound is canceled using a pair of microphones as in Patent Document 1, the sensitivity of the microphones deteriorates due to heat, secular change, and vibration, thereby reducing the howling prevention effect.

  Further, the electret condenser microphone Mp has a problem that it is easily destroyed by static electricity.

  The present invention has been made in view of the above-described reasons, and an object of the present invention is to provide a communication device that can suppress deterioration in sensitivity of a microphone due to heat, secular change, and vibration and does not reduce howling prevention effects.

The invention of claim 1 includes a speaker for outputting audio information transmitted from the outside, first outputs a sound signal by collecting a sound, a second microphone, the first, second microphone output a housing provided with a voice processing unit for transmitting to the outside by signal processing of each audio signal, the first microphone is disposed at a position closer to the speaker than the second microphone, the voice processing parts are by using the audio signal the first microphone output, the performs processing to reduce the speaker uttered the sound from the second sound signal by the microphone is output, the first, second microphone , respectively silicon microphone for applying a bias voltage between the silicon thin film and the electrodes are configured, are mounted on the same substrate, the speaker, in the housing The sound information transmitted from the outside is output from one side, a front air chamber surrounded by one side of the speaker and the inner surface of the housing is formed, and the front air chamber is formed. The substrate is disposed along an outer surface of the housing .

According to this invention, the sensitivity deterioration of the microphone due to heat, aging, and vibration can be suppressed, and the howling prevention effect is not reduced. In addition, power supply to the first and second microphones and attachment to the outer surface of the housing are facilitated.

  According to a second aspect of the present invention, in the first aspect, the first and second microphones are omnidirectional.

According to the present invention, the first and second microphones can be made compact .

The invention according to claim 3, characterized in claim 1 or 2, said on a surface of the housing defining a front air chamber, providing an opening for inserting the first microphone mounted before SL on the substrate According to the present invention, the first microphone can be attached to the speaker.

A fourth aspect of the present invention, in any one of claims 1 to 3, the surface of the housing forming the front air chamber, the pre-Symbol providing a recess for accommodating the second microphone mounted on a substrate It is characterized by.

  According to the present invention, the second microphone can be housed in the housing.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the sound processing unit is housed in the same package as the second microphone.

  According to the present invention, the communication device can be reduced in size and thickness.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the difference in sensitivity between the first and second microphones is within 3 dB.

  According to this invention, variation in the amount of cancellation of speaker sound by the sound processing unit is suppressed.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the outputs of the first and second microphones are amplified by the audio processing unit.

  According to the present invention, the amount of cancellation of speaker sound in the audio processing unit does not vary with frequency, and the howling prevention effect is stabilized in a wide frequency band.

As described above, according to the present invention, it is possible to suppress deterioration in sensitivity of the microphone due to heat, secular change, and vibration, and the effect of preventing howling is not reduced. In addition, power supply to the first and second microphones and attachment to the outer surface of the housing are facilitated.

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

(Embodiment)
The communication device A according to the present embodiment is shown in FIGS. 1 to 3, and is configured by accommodating a communication module MJ in a rectangular box-shaped device body A2 provided with a voice switch SW1. The apparatus main body A2 is formed, for example, by joining two resin molded members, and after housing the call module MJ, each joining member is joined by a fitting means or an adhesive.

  The call module MJ includes a housing A1 including a box-shaped base A11 having an opening on the front surface and a flat plate A10 covering the opening of the base A11. The housing A1 includes a speaker SP, a microphone board MB1, An audio processing unit 10 is provided. And the sound hole 12 mentioned later of housing A1 is arrange | positioned so as to oppose the some sound hole 60 drilled in the front surface of 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.

  The speaker SP includes a cylindrical yoke 20 (iron-based material having a thickness of about 0.8 mm, such as cold rolled steel plate (SPCC, SPKEN), electromagnetic soft iron (SUY)) formed of an iron-based material and having an open end. The yoke 20 is provided with a circular support 21 extending outward from the opening end. A cylindrical permanent magnet 22 (cylindrical neodymium magnet, residual magnetic flux density of 1.39 T to 1.43 T) is disposed in the cylinder of the yoke 20, and a dome-shaped diaphragm 23 (PEN (polyethylene naphthalate) or PEI ( The outer peripheral edge of a thermoplastic plastic (such as polyetherimide) is fixed to the edge surface of the support 21 (for example, a thickness of 35 μm to 50 μm). A cylindrical bobbin 24 is fixed to the rear surface of the diaphragm 23, and a voice coil 25 (a kraft paper tube wound with a polyurethane copper wire) is provided at the rear end of the bobbin 24. . 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. 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 the bobbin 24 is accompanied by the diaphragm 23. To vibrate in the front-rear direction. At this time, a sound corresponding to the audio signal is emitted from the diaphragm 23.

  And rib 11 is formed in the front inner side of plate A10 which diaphragm 23 of speaker SP opposes, and the end surface of convex part 21a which protruded from the outer peripheral end of circular support 21 of speaker SP to the front side, and The gasket 26 is placed on the rib 11. The mounting holes 27 provided at the four corners of the support 21 of the speaker SP are respectively placed on four bosses (not shown) formed at equal intervals on the inner surface of the plate A10, and screwed through the mounting holes 27. Then, the gasket 26 is in close contact with the boss 11, and the speaker SP is fixed in a state where the diaphragm 23 faces the inner surface of the plate A10. In addition, a plurality of sound holes 12 are formed in the place of the plate A10 facing the diaphragm 23.

  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. And a rear air chamber Br which is a space surrounded by the back surface side (yoke 20 side) of the speaker SP. The front air chamber Bf communicates with the outside through a plurality of sound holes 12 provided on the front surface of the plate A10. The rear air chamber Br becomes a space that is insulated (not communicated) with the front air chamber Bf because the gasket 26 of the support 21 of the speaker SP and the rib 11 on the inner surface of the housing A1 are in close contact with each other.

  Further, as shown in FIGS. 1 and 4, the housing A <b> 1 has one end separated from the inner wall surface along the inner wall surface of the base A <b> 11 surrounding the rear air chamber Br on the back surface of the speaker SP, and the other end continuous to the inner wall surface. The wall 41 is erected, and the end surface of the wall 41 abuts against the back surface of the plate A10, so that the wall 41, the inner wall surface of the base A11, and the back surface of the plate A10 are hollow acoustic tubes. 40 is formed, and the acoustic tube 40 is disposed in the small-volume rear air chamber Br. The acoustic tube 40 is a hollow closed tube having a rectangular cross-sectional shape bent along the inner wall surface of the rear air chamber Br, and is formed by opening one end (open end 40a) and closing the other end (closed end 40b). The inside of the pipe communicates with the rear air chamber Br through the open end 40a. An acoustic tube uses the fact that the input impedance becomes extremely small at the resonance frequency of the closed tube (the frequency at which the total length of the tube coincides with an odd multiple of a quarter wavelength). The reflected wave has a waveform whose phase is inverted with respect to the incident wave, and the incident wave and the reflected wave cancel each other, thereby reducing the sound wave propagating from the opening end 40a to the outside.

  Such an acoustic tube 40 is provided to shift the lowest resonance frequency of the speaker SP to the low frequency side and further increase the sound pressure level of the speaker SP. Is set to approximately a quarter wavelength of a low frequency (in the present embodiment, around 700 to 800 Hz), the sound quality and efficiency of the speaker SP can be improved even if the rear air chamber Br has a small capacity.

  Further, by forming the acoustic tube 40 continuously over a plurality of inner wall surfaces of the rear air chamber Br, the acoustic tube 40 provided in the small air rear chamber Br can be lengthened as necessary. Further, by forming the acoustic tube 40 in a bent shape, the acoustic tube 40 can be disposed in the small-capacity rear air chamber Br.

  Next, as shown in FIG. 5, the microphone substrate MB1 includes a module substrate 2 having both surfaces 2a and 2b. A pair of the microphone bare chip BC1 and ICKa1 and a pair of the microphone bare chip BC2 and ICKa2 are connected to the module substrate 2. And mounted between the bare chips BC1, ICKa1, and the wiring pattern (not shown) on the module substrate 2 and between the bare chips BC2, ICKa2 and the wiring pattern (not shown) on the module substrate 2 respectively. After each connection (wire bonding) with W, the shield case SC1 is mounted so as to cover the pair of bare chips BC1 and ICKa1, and the shield case SC2 is mounted so as to cover the pair of bare chips BC2 and ICKa2. BC1, ICKa1, and shield case SC1 Microphones M1 to be provided with a bare chip BC2, ICKa2, microphone M2 composed of the shield case SC2.

  The bare chip BC (bare chip BC1 or BC2) is formed by using the MEMS technology, and as shown in FIG. 6, a silicon 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 the silicon thin film 1d and an air gap 1e (for example, 3 μm), and a pad 1g for outputting an audio signal is provided to constitute a capacitor type silicon microphone. Yes. A bias voltage is applied between the silicon thin film 1d and the electrode 1f from the outside, and an acoustic signal from the outside vibrates the silicon thin film 1d, whereby the capacitance between the silicon thin film 1d and the electrode 1f is increased. The charge amount changes to change, and a current corresponding to the acoustic signal flows from the pads 1g, 1g along with the change in the charge amount. In this bare chip BC, the silicon substrate 1 b is die-bonded on the module substrate 2, and in particular, the silicon thin film 1 d of the bare chip BC 2 faces the sound hole F 2 formed in the module substrate 2. Unlike an electret condenser microphone, such a silicon microphone does not need to be charged with a diaphragm, so that sensitivity deterioration due to heat, aging and vibration is small, and it is difficult to be destroyed by static electricity.

  The microphone M1 uses the bottom surface side of the shield case SC1 with the sound hole F1 as a sound collecting surface, and the microphone M2 uses the mounting surface side with respect to the module substrate 2 with the sound hole F2 as a sound collecting surface. The sound collecting surfaces are provided on both sides of the module substrate 2 in opposite directions. Since the microphone substrate MB1 configured in this manner has both the microphones M1 and M2 mounted on the one surface 2a of the module substrate 2, the thickness of the microphone substrate MB1 can be reduced.

  FIG. 7A is a plan view of the microphone board MB1 as viewed from the one surface 2a side of the module board 2. The module board 2 has a rectangular part 2f in which the microphone M1 is arranged and a rectangular part 2g in which the microphone M2 is arranged. And a connecting portion 2h that connects the rectangular portions 2f and 2g, and the rectangular portion 2g is formed larger than the rectangular portion 2f. A negative power supply pad P1, a positive power supply pad P2, an output 1 pad P3, and an output 2 pad P4 are provided along the edge of the rectangular portion 2g.

  As shown in FIG. 7B, 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. A power supply voltage 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.

  In this way, the power supply voltages of the microphones M1 and M2 are 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 also used by the negative power supply pad P1, thereby The number can be reduced and the configuration is simplified.

  Next, the operation of the microphone substrate MB1 will be described.

  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.

  ICKa (ICKa1 or ICKa2) has the circuit configuration of FIG. 8, and is a constant IC composed of a chip IC that converts a power supply voltage + V (for example, 5V) supplied from power supply pads P1 and P2 into a bias voltage Vr (for example, 12V). A voltage circuit Kb is provided, and a bias voltage Vr is applied between the silicon thin film 1d and the electrode 1f (see FIG. 6) of the bare chip BC via a resistor R11, and a connection midpoint between the resistor R11 and the bare chip BC is a capacitor C11. To the gate terminal of the junction type J-FET element S11. The drain terminal of the J-FET element S11 is connected to the power supply voltage + 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.

  The microphone board MB1 can efficiently configure the signal lines and the power supply lines by performing signal transmission and power supply via the wiring pattern on the module board 2 as described above, and can be attached to the outer surface of the housing A1. Become. In the present embodiment, the one surface 2a of the module substrate 2 is fixed along the outer front surface of the housing A1 by a thermosetting adhesive or a thermoplastic adhesive such as hot melt.

  The microphones M1 and M2 are non-directional and are small in size, but the microphone M1 is inserted through the opening 13 on the front surface of the housing A1 so that the sound collection surface faces the front air chamber Bf, and the bottom surface of the shield case SC1. The sound hole F1 of the microphone M1 drilled in is opposed to the center of the diaphragm 23 of the speaker SP and collects the sound from the speaker SP transmitted through the sound hole F1. Furthermore, by making the sound collection surface of the microphone M1 face the center of the diaphragm 23 of the speaker SP, the microphone M1 can easily collect the sound emitted by the speaker SP in a correct phase.

  The microphone M2 is fitted into a recess 14 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 located outside (frontward) the housing A1 in the output direction of the speaker SP. Therefore, the voice from the speaker located in front of the communication device A, which is transmitted through the sound hole F2, is collected. If the distances from the center of the speaker SP to the centers of the microphones M1 and M2 are X1 and X2, respectively, X1 <X2.

  Further, the rear air chamber Br facing the back surface of the speaker SP is sealed in the housing A1, so that sound radiated from the back surface of the speaker SP is difficult to leak from the rear air chamber Br, and the speaker SP and the microphone M2 are not connected. Acoustic coupling is reduced. Furthermore, the sound radiated from the back surface of the speaker SP (the back surface of the diaphragm 23) has a phase reversed from that of the sound radiated from the surface of the speaker SP (the surface of the diaphragm 23). When the generated sound circulates forward, the sound radiated from the surface of the speaker SP cancels each other, the radiated sound pressure of the speaker SP decreases, and the speaker in front cannot hear the sound emitted by the speaker SP. However, since the sound radiated from the back surface of the speaker SP is difficult to leak to the outside of the housing A1 as described above, a decrease in the radiated sound pressure of the speaker SP due to the wraparound is prevented.

  Further, since the concave portion 14 in which the microphone M2 is accommodated is a separated space that does not communicate with the rear air chamber Br, the microphone M2 is more difficult to collect the sound emitted by the speaker SP, and the speaker SP and the microphone M2 are separated. The acoustic coupling is further reduced. That is, with the above configuration, the sound emitted from the speaker SP and the sound emitted from the speaker are separated and collected by the microphones M1 and M2.

  Further, when the microphone substrate MB1 is disposed in the housing A1, it is difficult to maintain the spatial insulation between the front air chamber Bf and the rear air chamber Br, but the microphone substrate MB1 is disposed in the housing as in the present embodiment. By attaching to the outer surface of A1, the spatial insulation between the front air chamber Bf and the rear air chamber Br can be maintained.

  And in this embodiment, in order to prevent the howling which generate | occur | produces when the microphones M1 and M2 pick up the audio | voice output of the speaker SP, it has the following structures.

  First, as shown in FIG. 9, the signal processing unit 10 e housed in the audio processing unit 10 includes an amplification circuit 30 that non-inverts and amplifies the output of the microphone M <b> 1, and an audio band (300 to 4000 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 at frequencies other than (300 to 4000 Hz), and an adder circuit 35 that adds outputs of the delay circuit 32 and the band-pass filter 34 are provided.

  10 to 13 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. First, when the distances from the center of the speaker SP to the centers 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 direction of the microphones M1 and M2. The amplitude of the microphone M2 is small and the sound wave delay time [Td = (X2-X1) / Vs] (Vs is the speed of sound) corresponding to the difference (X2-X1) in the distance between the two microphones M1, M2 and the speaker SP. The phase of the output Y21 is delayed (see FIGS. 10A and 10B).

  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, M2 and the speaker SP is performed to match the output levels of the two microphones M1, M2 with respect to the sound from the speaker SP (FIG. 11 ( a) (b)). In the present embodiment, the amplification factor of the amplifier circuit 30 is approximately 1, and the amplifier circuit 30 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. 12A and 12B).

  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. 13A to 13C). That is, in the output Ya, the sound component from the speaker SP is reduced.

  On the other hand, for the sound uttered by the speaker H in front of the microphones M1, M2, the amplitude of the output Y21 of the microphone M2 arranged forward is larger than the amplitude of the output Y11 of the microphone M1. 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.

  As described above, the signal processing unit 10e prevents howling by canceling after the phases and amplitudes of the speaker sounds collected by the microphones M1 and M2 coincide with each other. By using the above-described silicon microphone (see FIG. 6) that does not require the diaphragm to be charged as M2, the sensitivity deterioration of the microphone due to heat, aging and vibration is suppressed, and the effect of preventing howling is not reduced. Yes. In addition, the microphones M1 and M2 are less likely to be damaged by static electricity, and the reliability is excellent.

  In addition, the human audible sound pressure level is 0 dB to 140 dB (sound pressure: 0.00002 to 200 Pa), and humans clearly have no sound change unless the sound changes more than about 6 dB (1/2 or 2 times). Cannot recognize the difference in size. FIG. 14 shows the amount of cancellation of speaker sound with respect to the sensitivity difference between microphones M1 and M2 (sensitivity of microphone M1−sensitivity of microphone M2). If the sensitivity difference between microphones M1 and M2 is within 3 db (in FIG. 14). Range Z1), the amount of cancellation of the speaker sound by the signal processing unit 10e is 6 dB or more, and a human can clearly recognize the difference in the amount of cancellation of the speaker sound.

  Therefore, in this embodiment, the sensitivity difference between the microphones M1 and M2 is maintained within 3 dB. Therefore, the variation in the cancellation amount can be suppressed without reducing the cancellation amount of the speaker sound to 6 dB or less.

  Further, as shown in FIG. 15, the output characteristic Yb of the microphone with a built-in preamplifier changes in gain and phase according to the frequency, so that the amount of cancellation of the speaker sound in the signal processing unit 10e varies depending on the frequency, and the howling prevention effect is obtained. It will decline. On the other hand, since the output characteristic Ya of the microphone not including the preamplifier has a gain and a phase that are substantially constant with respect to the frequency, the amount of cancellation of the speaker sound in the signal processing unit 10e does not vary depending on the frequency, and the howling prevention effect Is stable in a wide frequency band. Therefore, in the present embodiment, the microphones M1 and M2 themselves do not include a preamplifier for amplifying the collected sound signal, and the sound signals are amplified by the amplifier circuits 30 and 33 provided in the signal processing unit 10e. ing.

  Furthermore, in the audio processing unit 10, the audio switch unit 10b is arranged on the transmission line of the signal received, and the audio switch unit 10c is arranged on the transmission line of the signal transmitted (see FIG. 3). 10b and 10c compare the levels of the input signals with each other, and the voice switch unit with the smaller input signal level has a loss amount (for example, a loss amount of 48 dB) on the transmission line by the variable loss means provided inside. Give. Therefore, a signal having a lower level of the received signal and the transmitted signal is attenuated and the howling margin is further increased (for example, an increase of 48 dB), so that further howling prevention is achieved.

  Further, although the sound processing unit 10 is disposed in the housing A1 (see FIG. 1), as shown in FIG. 16, it may be mounted in the shield case SC2 of the microphone M2 on the microphone board MB1. Further, the communication device A can be reduced in size and thickness.

  Further, although the phase difference and amplitude difference of the outputs of the microphones M1 and M2 with respect to the sound from the speaker SP have frequency dependence, the signal processing unit 10e separates the outputs of the microphones M1 and M2 into a plurality of frequency bands. A configuration may be adopted in which speaker sound is canceled for each frequency band. As means for separating the outputs of the microphones M1 and M2 into a plurality of frequency bands, there are a configuration using a plurality of bandpass filters, a configuration for estimating a signal in another frequency band from a signal in a certain frequency band, and the like. .

  Further, the signal processing unit 10e uses the delay circuit 32 to match the phases of the outputs of the microphones M1 and M2 with respect to the speaker sound, but the A / D conversion means A / D conversion means provided at the outputs of the microphones M1 and M2 The D conversion timing may be shifted by the delay time Td to match the phases of the outputs of the microphones M1 and M2.

  In the present embodiment, voice signals are exchanged between the call devices A using a wired communication system via the information line Ls. However, by providing the call devices A with known wireless communication means, Voice signals may be exchanged using a communication method.

It is side surface sectional drawing which shows the structure of embodiment. (A) (b) It is a perspective view same as the above. It is a circuit block diagram same as the above. It is a partially exploded perspective view of the call module 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 amount of the speaker sound by a signal processing part same as the above. It is a figure which shows the output characteristic of a microphone same as the above. It is side surface sectional drawing which shows another structure of a microphone substrate same as the above. It is side surface sectional drawing which shows schematic structure of the conventional electret condenser microphone.

A Calling device MJ Calling module A1 Housing SP Speaker M1, M2 Microphone 10 Audio processing unit

Claims (7)

A speaker for outputting audio information transmitted from the outside, first, the second microphone, the first, each audio signal a second microphone output signal processing for outputting a sound signal by collecting a sound And a housing provided with a voice processing unit that transmits to the outside,
The first microphone, the are located closer to the speaker than the second microphone, the audio processing unit uses the audio signal the first microphone output and the second microphone output from the audio signal to perform processing for reducing the sound speaker uttered,
It said first, second microphones, respectively silicon microphone for applying a bias voltage between the silicon thin film and the electrodes are configured, are mounted on the same substrate,
The speaker is disposed in the housing, outputs audio information transmitted from the outside from one surface side, and forms a front air chamber surrounded by the one surface side of the speaker and the inner surface of the housing,
A communication device, wherein the substrate is disposed along an outer surface of the housing forming the front air chamber .   The call device according to claim 1, wherein the first and second microphones are non-directional. 3. The communication device according to claim 1, wherein an opening through which the first microphone mounted on the substrate is inserted is provided on a surface of the housing forming the front air chamber. 4. The communication device according to claim 1, wherein a concave portion for accommodating the second microphone mounted on the substrate is provided on a surface of the housing forming the front air chamber. 5. The call device according to any one of claims 1 to 4, wherein the voice processing unit is housed in the same package as the second microphone. 6. The communication device according to claim 1, wherein a sensitivity difference between the first and second microphones is within 3 dB. 7. The communication device according to claim 1, wherein outputs of the first and second microphones are amplified by the voice processing unit.

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