JP4989372B2 - Telephone device - Google Patents

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.

  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, a first microphone that collects sound and outputs a sound signal, and a speaker far from the first microphone with respect to the speaker, the sound is collected and the sound signal is collected. And a sound processing unit for removing the sound signal of the first microphone from the sound signal of the second microphone and transmitting the sound signal to the outside, and the diaphragm of the speaker has a phase inversion axis as a boundary As described above, a divided vibration is generated in which two regions having opposite phases are generated, and the first and second microphones are arranged in parallel along the axial direction of the phase inversion axis.

  According to the present invention, howling can be prevented without reducing the amount of cancellation of speaker sound even when the diaphragm of the speaker vibrates in a divided manner.

  According to a second aspect of the present invention, in the first aspect, the axial direction of the phase inversion axis is determined by a weight balance of the diaphragm.

  According to this invention, the axial direction of the phase inversion axis can be determined by appropriately setting the weight balance of the diaphragm.

  According to a third aspect of the present invention, in the first or second aspect, the speaker wiring is fixed to the diaphragm, and the axial direction of the phase inversion axis is determined at least by a fixed position of the speaker wiring.

  According to the present invention, the axial direction of the phase inversion axis can be determined by appropriately setting the fixed position of the speaker wiring.

  A fourth aspect of the present invention is the rear air chamber according to any one of the first to third aspects, wherein the speaker outputs sound from one side to the outside and the other side of the speaker is spatially insulated from the outside. Is formed.

  According to the present invention, the reverse phase sound radiated from the back surface of the speaker to the rear air chamber hardly leaks out of the rear air chamber, and the sound processing unit performs a howling prevention process by collecting the reverse phase sound. The adverse effect of can be suppressed.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the sound collection surface of the first microphone faces the diaphragm of the speaker.

  According to the present invention, the sound pressure difference between the first and second microphones increases with respect to the speaker sound and the speaker's call voice, and the amount of cancellation of the speaker sound increases.

  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 microphone can be positioned with respect to the phase inversion axis efficiently and accurately, and the amount of cancellation of speaker sound is stabilized.

  According to a seventh aspect of the present invention, in the sixth aspect, the speaker is attached to the housing and outputs sound from one side to the outside of the housing, the substrate is attached to the outer surface of the housing, and the first microphone is provided. The sound collecting surface of the second microphone is opposed to the diaphragm of the speaker, and the sound collecting surface of the second microphone is arranged outside the housing.

  According to the present invention, it is difficult to maintain the spatial insulation of the rear air chamber when the substrate is disposed in the housing, but the spatial insulation of the rear air chamber is achieved by attaching the substrate to the outer surface of the housing. Can be maintained.

  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 1)
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. And a rear air chamber Br which is a space surrounded by the back 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 empty 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 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.

  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 1b is die-bonded on the module substrate 2. In particular, the Si thin film 1d of the bare chip BC2 faces the sound hole F2 formed in the module substrate 2.

  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. 6A 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.

  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.

  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.

  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.

  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 this embodiment, one surface 2a of the module substrate 2 is arranged along the outer front surface of the housing A1, and 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 shield The sound hole F1 of the microphone M1 formed in the bottom surface of the case SC1 faces the diaphragm 23 of the speaker SP, and the sound emitted from the speaker SP can be reliably collected through the sound hole F1.

  Further, the microphone M2 is fitted into the 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 opposed to the sound hole 61 formed in the front surface of the apparatus main body A2. Furthermore, since it faces the outside (front) of the housing A1 toward the output direction of the speaker SP, the voice from the speaker located in front of the communication device A that is transmitted through the sound hole F2 is surely received. Sound can be collected.

  Furthermore, 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 difficult to collect the sound emitted by the speaker SP, and the sound between the speaker SP and the microphone M2 is difficult to collect. Bonding is further reduced. That is, with the above configuration, the sound emitted by the speaker SP and the sound emitted by the speaker are separated and collected by the microphones M1 and M2.

  If 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. However, as in the present embodiment, the microphone substrate MB1 is disposed in the housing A1. By attaching to the outer surface, the spatial insulation between the front air chamber Bf and the rear air chamber Br can be maintained.

  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. In this embodiment, the sound output from the speaker SP is picked up by the microphones M1 and M2. In order to prevent howling, 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, 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 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.

  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. Thus, the microphone M2 can be arranged in the vicinity of the speaker SP, that is, in the vicinity of the front air chamber Bf, and the communication device A can be downsized.

  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, 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 equal to or higher than a certain frequency, a plurality of vibration regions having different phases generate divided vibrations generated in the diaphragm 23. In the present embodiment, since the speaker wiring W is fixed with resin in the radial direction along the back surface of the circular diaphragm 23, the weight balance of the diaphragm 23 becomes unbalanced with respect to the diameter, and the predetermined frequency f1. In the vicinity, as shown in the amplitude velocity distributions of FIGS. 14A and 14B, the phases are opposite to each other with the phase inversion axis Za formed in the diameter direction substantially along the fixing direction of the speaker wiring W as a boundary. Two vibration regions G1 and G2 are generated in the diaphragm 23. 13 and 14A are perspective views as seen from the surface side of the diaphragm 23. FIG.

The diaphragm 23 of the speaker SP has a circular shape, and its outer peripheral edge is fixed to the edge surface of the support 21 (see the schematic diagram of FIG. 15). Radius r (cm) to peripheral edge, thickness t (cm) of diaphragm 23, density ρ (g / cm ³ ) of diaphragm 23, Poisson's ratio σ of diaphragm 23, Young's modulus E ( dyne / cm ² ), the lowest resonance frequency fo of the speaker SP when the speaker SP is attached to a baffle plate (not shown) having an infinite size is expressed by [Equation 1] and is divided into two. The frequency f1 at which the vibration occurs is expressed by [Equation 2]. The minimum resonance frequency fo is an ideal characteristic that is the same as that of the speaker SP alone.

FIG. 16 shows actual sound pressure characteristics when the speaker SP is attached to a baffle plate (not shown) having an infinite size. In this embodiment, the range of the lowest resonance frequency fo is 500 to 600 Hz. The range of the frequency f1 at which the split vibration of two splits is generated is 800 to 900 Hz. Note that the frequency f1 with respect to the lowest resonance frequency fo in FIG. 16 is different from the theoretical calculation of the above [Equation 2].
(1) In order to increase the rigidity of the diaphragm 23, the actual diaphragm 23 is formed with uneven ribs, and the thickness t of the diaphragm 23 is calculated to be constant as in the theoretical calculation of [Equation 2]. The results are different.
(2) Since the outer peripheral edge of the diaphragm 23 is fixed to the support 21 with an adhesive, the fixed state is not uniform.
(3) Since the speaker wiring W is fixed on the diaphragm 23 with resin, the mass of the diaphragm 23 is not uniform.
This is because of the reason.

  Next, the effect of the piston motion or the divided vibration of the diaphragm 23 on the speaker sound canceling process will be described. 17, FIG. 18, and FIG. 20 show a form in which the microphone M1 is disposed on the side of the speaker SP for the sake of explanation.

  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 the vicinity of 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.

  Then, an amplitude difference generated in each sound signal emitted from the vibration region G1 and collected by the microphones M1 and M2, and an amplitude difference generated in each sound signal emitted from the vibration region G2 and collected by the microphones M1 and M2. 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 radiated from the vibration regions G1 and G2, and the howling prevention effect is reduced. End up.

  FIGS. 19A to 19C show characteristics after adjusting the gain and delay time of the signal processing unit 10e so that the amount of cancellation of the speaker sound becomes substantially zero at 2 KHz in the configuration of FIG. The signals Y14 and -Y23 (inverted signals of Y23) input to the adder circuit 35 have a sound pressure level difference (FIG. 19A) and a phase difference (FIG. 19B) near the frequency f1 (800 to 900 Hz). ) Greatly fluctuates, and the amount of cancellation of the speaker sound in the signal Ya output from the adder circuit 35 (FIG. 19C) is reduced to the minimum level in the vicinity of the frequency f1, which adversely affects howling prevention.

  Therefore, in the present embodiment, the arrangement direction Zb of the microphones M1 and M2 is the direction along the axial direction of the phase inversion axis Za, and the microphones M1 and M2 are on the phase inversion axis Za (vibration) in the amplitude velocity distribution of FIG. Not only on the plate 23 but also on the extended line). Thus, the distances from the vibration areas G1, G2 to the microphone M1 or M2 are the same, and there is no difference in the vibration areas G1, G2 with respect to the microphones M1, M2 (in FIG. 20, the distance X31 = X32, distance X41 = X42). That is, there is a gap between the microphones M1 and M2 between the sound wave emitted from the vibration areas G1 and G2 and collected by the microphone M1 and the sound wave emitted from the vibration areas G1 and G2 and collected by the microphone M2. Only an amplitude difference and a phase difference due to the distance difference X10 occur.

  Therefore, the above-described initial phase difference exists between the sound wave emitted from the vibration region G1 and collected by the microphones M1 and M2 and the sound wave emitted from the vibration region G2 and collected by the microphones M1 and M2. Although there is no need to consider the distance difference X20 between the vibration regions G1 and G2 with respect to the microphones M1 and M2 as shown in FIG. 18, the signal processing unit 10e increases the distance difference X10 between the microphones M1 and M2 as described above. If the gain and the delay time are adjusted based on this, both sound waves radiated from the vibration regions G1 and G2 can be canceled, and howling is prevented. In particular, in the configuration in which the microphone M1 is disposed in the vicinity of the speaker SP, the influence of the distance difference X20 between the vibration regions G1 and G2 on the microphones M1 and M2 becomes large, so the configuration in FIG. 20 is effective.

  Further, by attaching the microphone board MB1 on which the microphones M1 and M2 are mounted to the outer surface of the housing A1, the microphones M1 and M2 can be positioned with respect to the phase reversal axis Za of the diaphragm 23 efficiently and accurately. The amount of speaker sound cancellation by the processing unit 10e is stabilized.

  FIGS. 21A to 21C show characteristics after adjusting the gain and delay time of the signal processing unit 10e so that the amount of cancellation of speaker sound becomes substantially zero at 2 KHz in the configuration of FIG. The signals Y14 and -Y23 (inverted signals of Y23) input to the adder circuit 35 are the sound pressure level difference (FIG. 20 (a)) and phase difference (FIG. 20 (b)) near the frequency f1 (800 to 900 Hz). ) Does not fluctuate greatly, and the amount of cancellation of the speaker sound (FIG. 20C) in the signal Ya output from the adder circuit 35 is not reduced near the frequency f1, and howling is prevented.

  In FIG. 20, the microphones M1 and M2 are arranged so as to be positioned on the phase inversion axis Za. However, the microphones M1 and M2 do not have to be strictly on the phase inversion axis Za and are orthogonal to the phase inversion axis Za. You may arrange | position so that it may shift | deviate to the direction to do. In this case, the deviation width with respect to the phase inversion axis Za is set to a range that does not substantially affect the amount of cancellation of the speaker sound.

  Note that the microphones M1 and M2 are arranged with respect to the speaker SP in any of FIGS. 22A to 22C, and the arrangement direction Zb of the microphones M1 and M2 is the direction along the axial direction of the phase inversion axis Za. By doing so, the same effect can be obtained. In FIG. 22A, the microphone M1 is opposed to the center of the diaphragm 23 of the speaker SP, and the microphone M2 is disposed on the side of the speaker SP. In FIG. 22B, the microphone M1 is opposed to the periphery of the diaphragm 23 of the speaker SP, and the microphone M2 is disposed on the side of the speaker SP. In FIG. 22C, the microphones M1 and M2 are both disposed on the side of the speaker SP.

(Embodiment 2)
As shown in FIG. 23, the diaphragm 23 of the speaker SP of the present embodiment is formed in a substantially oval shape, and the phase inversion axis Za at the time of divided vibration occurs on the minor axis of the ellipse. Therefore, as shown in FIG. 24, by arranging the microphones M1 and M2 in the minor axis direction of the diaphragm 23, howling can be prevented without reducing the amount of cancellation of the speaker sound near the frequency f1. .

  Other configurations are the same as those of the first embodiment, and a description thereof will be omitted.

It is side surface sectional drawing which shows the structure of the communication apparatus of Embodiment 1. (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 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 divided vibration same as the above. It is a top view which shows the division 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 same as the above. It is a figure which shows the propagation of the sound wave at the time of the division vibration same as the above. (A)-(c) It is a figure which shows each characteristic at the time of the divided vibration same as the above. It is a figure which shows the propagation of the sound wave at the time of the division vibration same as the above. (A)-(c) It is a figure which shows each characteristic at the time of the divided vibration same as the above. (A)-(c) It is a figure which shows the example of arrangement | positioning of the microphone with respect to a speaker. (A) (b) It is a figure which shows the substantially oval speaker of Embodiment 2. FIG. It is a figure which shows arrangement | positioning of a microphone same as the above.

Explanation of symbols

A Communication device MJ Communication module A1 Housing M1, M2 Microphone SP Speaker 23 Diaphragm Za Phase reversal axis

Claims (7)

Speakers,
A first microphone that collects sound and outputs a sound signal;
A second microphone arranged at a position farther than the first microphone relative to the speaker and collecting voice and outputting a voice signal;
An audio processing unit for removing the audio signal of the first microphone from the audio signal of the second microphone and transmitting the same to the outside;
The diaphragm of the speaker generates a split vibration in which two regions having opposite phases with respect to the phase inversion axis are generated, and the first and second microphones are arranged in parallel along the axial direction of the phase inversion axis. A call device characterized by the above.   2. The communication device according to claim 1, wherein an axial direction of the phase inversion axis is determined by a weight balance of the diaphragm.   3. The communication device according to claim 1, wherein the speaker wiring is fixed to the diaphragm, and an axial direction of the phase inversion axis is determined at least by a fixing position of the speaker wiring.   The speaker outputs sound from one side to the outside, and a rear air chamber that is spatially insulated from the outside is formed on the other side of the speaker. The communication device described.   5. The communication device according to claim 1, wherein a sound collection surface of the first microphone is opposed to a diaphragm of the speaker.   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.   The speaker is attached to the housing and outputs sound from the one surface side to the outside of the housing, the substrate is attached to the outer surface of the housing, and the sound collecting surface of the first microphone faces the diaphragm of the speaker. The call device according to claim 6, wherein the sound collection surface of the second microphone is arranged toward the outside of the housing.

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