JP2008294995A - Talking device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a talking device capable of preventing howling and improving sound quality and efficiency. <P>SOLUTION: A talking module MJ has: a housing A1; a speaker SP that is attached to the housing A1 and outputs sound information to the outside of the housing from one surface side; a rear air space Br that is a space formed at the other surface side of the speaker SP in the housing; a microphone M1 outputting a sound signal, where collected sound is converted to an electric signal; a microphone M2 that is arranged at a position far from the speaker SP as compared with the microphone M1 and outputs a sound signal, where collected sound is converted to an electric signal; a sound processing section 10 for eliminating the sound signal collected by the microphone M1 from the sound signal collected by the microphone M2 for transmitting to the outside; and a communication section 4 for allowing the rear air space Br to communicate with the outside of the housing A1 via an opening 4a provided in the housing A1. <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 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. It is possible to remove the voice component from the speaker to prevent howling, and 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)

  In recent years, telephone devices have become thinner and thinner for miniaturization, and the capacity of housings for housing speakers has become smaller. In particular, if the volume of the rear air chamber, which is the space on the back side of the speaker, is reduced, the sound pressure radiated from the speaker is lowered, the lowest resonance frequency of the speaker is shifted to the higher frequency side, and the sound quality and efficiency of the speaker are deteriorated. was there.

  The present invention has been made in view of the above reasons, and an object of the present invention is to provide a communication device that can realize howling prevention, improvement in sound quality, and efficiency.

  The invention of claim 1 includes a housing, a speaker that is attached to the housing and outputs audio information from one side to the outside of the housing, and a rear chamber that is a space formed on the other side of the speaker in the housing. A first microphone that collects sound and outputs an audio signal; a second microphone that is disposed farther than the first microphone with respect to the speaker and that collects sound and outputs an audio signal; An audio processing unit that removes the audio signal of the first microphone from the audio signal of the second microphone and transmits the signal to the outside, and a communication unit that continuously connects the rear air chamber and the outside of the housing through an opening provided in the housing It is characterized by providing.

  According to the present invention, howling prevention processing can be performed by the voice processing unit. Furthermore, since the lowest resonance frequency of the speaker is shifted to the low frequency side by the communication portion and the sound pressure level of the speaker is increased, the sound quality and efficiency of the speaker are improved. That is, in the communication device, it is possible to realize howling prevention, sound quality and efficiency.

  According to a second aspect of the present invention, in the first aspect, the first microphone is disposed such that a sound collection surface faces the diaphragm of the speaker.

  According to the present invention, the amplitude difference between the outputs of the first and second microphones with respect to the sound emitted from the speaker can be increased, and the speaker sound canceling process can be reliably performed by the sound processing unit.

  According to a third aspect of the present invention, in the first or second aspect, the distance between the second microphone and the opening is set to be 10 times or more the shortest distance between the second microphone and the diaphragm of the speaker. It is characterized by.

  According to this invention, it is possible to suppress a reduction in the amount of cancellation of speaker sound due to sound waves radiated from the communicating portion.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, a sound absorbing material is disposed in the communication portion.

  According to the present invention, it is possible to absorb sound waves (especially high frequency bands) other than the frequency band enhanced by the communication part, and to reduce the adverse effect on the cancellation amount of the speaker sound due to the sound wave radiated from the communication part.

  As described above, the present invention has the effects of preventing howling and improving sound quality and efficiency.

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

(Embodiment 1)
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 body A10 having an opening on the rear surface and a planar cover A11 covering the opening of the body A10. The housing A1 includes a speaker SP, a microphone board MB1, and a sound processing unit. 10 is provided. A diaphragm 23 described later of the speaker SP is disposed so as to face 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, echo cancellation 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 via the information line Ls is received by the communication unit 10a, amplified by the amplification unit 10d via the echo cancellation 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, the signal passes through the echo cancel 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.

  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 (yoke 20 side) of the speaker SP, is formed, and the front air chamber Bf communicates with the outside through a plurality of sound holes 12 provided on the front surface of the housing A1. is doing. 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, and the cover A11 has a body A10. By being in close contact with the rear opening, a sealed space that is insulated from the outside is formed.

  Further, an opening 4a is formed in the front surface of the housing A1, and a cylindrical communication portion 4 having both ends opened from the opening 4a into the rear air chamber Br is formed. The rear air chamber Br is continuous to the outside of the housing A1 through the communication portion 4 and the opening 62. The opening 62 is formed in the front surface of the apparatus main body A2.

  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. 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, 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. 8, the signal processing unit 10 e housed in the audio processing unit 10 includes an amplifier 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 amplifier 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.

  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, 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.

  On the other hand, for the sound uttered by the speaker H in front of the microphones M1 and M2, the amplitude of the sound signal Y21 of the microphone M2 whose sound collection surface is arranged toward the speaker H is larger than the amplitude of the output Y11 of the microphone M1. growing. 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 microphone M2 has the sound collection surface facing the outside of the housing A1, and the sound collection surface of the microphone M2 is directed in the same direction as the output of the speaker SP, the acoustic coupling between the speaker SP and the microphone M2 is reduced, and the microphone M2 is a speaker. It becomes difficult to collect the sound emitted by the SP, and the microphone M2 can be disposed in the vicinity of the speaker SP, that is, in the vicinity of the front air chamber Bf, so that the communication device A can be reduced in size.

  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.

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

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

  Specifically, the echo cancellation units 10b and 10c are configured by a speaker SP-microphone M1, M2-signal processing unit 10e-echo cancellation unit 10c-communication unit 10a-echo cancellation unit 10b-amplification 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.

  And the communication apparatus A of this embodiment has improved the sound quality and efficiency of the speaker SP by providing the said communication part 4 in the front surface of housing A1, and hereafter, the effect | action of the communication part 4 is demonstrated. First, 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. Is reversed (hereinafter, the phase of the sound radiated from the surface of the speaker SP is referred to as a positive phase, and the phase of the sound radiated from the back surface of the speaker SP is referred to as an opposite phase), but is radiated to the rear chamber Br. The sound of the opposite phase is reversed when passing through the communication part 4 and is led out of the housing A1 as a positive phase. This communication part 4 is formed in a length and shape that reverses the sound of the opposite phase radiated to the rear air chamber Br to the normal phase. Then, by appropriately setting the frequency characteristics of the sound whose phase is inverted depending on the length and shape of the communication portion 4, the lowest resonance frequency of the speaker SP shifts to the low frequency side (for example, about 700 Hz), and further, the speaker SP. Therefore, the sound quality and efficiency of the speaker SP are improved.

Note that the minimum resonance frequency fo of the speaker is generally equivalent to the equivalent mass (diaphragm, coil, additional air mass) Mo of the vibration system of the speaker, the stiffness So such as an edge supporting the same, and the air in the rear air chamber Br. And the stiffness Sc of
fo = {1 / (2π)} · √ {(So + Sc) / Mo}
It is represented by

  FIG. 13 shows the frequency characteristic of the radiated sound pressure in front of the speaker SP. FIG. 13 (a) shows the characteristic when the communication part 4 is provided in the housing A1, and FIG. 13 (b) shows the communication part 4. Each characteristic when the housing A1 is sealed by sealing is shown.

  In FIG. 13A, the characteristic Y1a is a sound radiated from the front surface of the diaphragm 23 of the speaker SP, the characteristic Y1b is a sound radiated from the rear surface of the diaphragm 23 of the speaker SP through the communicating portion 4, and the characteristic Y1 is , The sound radiated to the front surface of the telephone conversation device A in which the characteristic Y1a and the characteristic Y1b are combined. First, there is a point where the sound pressure level of the radiated sound (characteristic Y1a) from the front surface of the speaker SP drops at the low frequency f1, but the sound pressure level of the radiated sound (characteristic Y1b) from the communicating portion 4 has the maximum sound pressure level at the low frequency f1. It becomes. And the sound (characteristic Y1) radiated to the front surface of the communication device A is a combination of both the sound radiated from the speaker SP and the communication part 4, and the characteristic Y1 is the sealing shown in FIG. 13 (b). Compared to the characteristic Y2 in the case of using a mold type housing, the high sound pressure level is expanded to a low frequency range, and the characteristic is flatter over a wide frequency band.

  However, in the present embodiment, the pair of microphones M1 and M2 are used to reduce the speaker sound from the transmitted signal to prevent howling, and the speaker sound radiated through the communication unit 4 is transmitted to both microphones M1 and M2. When M2 collects the sound, the speaker sound radiated through the communication unit 4 remains in the output Ya of the adder circuit 35, so that the amount of cancellation of the speaker sound is reduced, which may adversely affect the howling prevention effect. .

  In the output of the microphone M1 provided facing the speaker SP, the radiated sound from the communication portion 4 is smaller than the radiated sound from the front surface of the speaker SP, and the influence of the radiated sound from the communication portion 4 is small. On the other hand, in the output of the microphone M2 provided forward on the side of the speaker SP, the radiated sound from the communication unit 4 is substantially the same level as the radiated sound from the front surface of the speaker SP, and the radiated sound from the communication unit 4 The effect of. In the speaker sound reduction processing by the signal processing unit 10e, the operations of the amplifier circuits 30 and 33 and the delay circuit 32 are set for the radiated sound from the front surface of the speaker SP. The speaker sound radiated through the communication part 4 remains.

  Therefore, in order to suppress a reduction in the amount of cancellation of the speaker sound due to the radiated sound from the communication unit 4, the ratio of the radiated sound from the communication unit 4 to the radiated sound from the front surface of the speaker SP collected by the microphone M2 is reduced. It will be necessary. FIG. 14 shows the sound pressure difference between the radiated sound from the front surface of the speaker SP collected by the microphone M2 and the radiated sound from the communication portion 4 [radiated sound from the front surface of the speaker SP−radiated sound from the communication portion 4]. 2 is a graph in which the amount of cancellation of speaker sound in the signal processing unit 10e is plotted on the vertical axis, and the sound pressure difference between the sound emitted from the front surface of the speaker SP collected by the microphone M2 and the sound emitted from the communication unit 4 It can be seen that a sufficient speaker sound cancellation amount is obtained when the communication portion 4 is 20 dB or more (in FIG. 14, the communication portion 4 has a canceling amount when the communication portion 4 is provided by setting the sound pressure difference to 20 dB or more. The amount of cancellation when there is no cancellation can be reduced to about 1 dB from 20 dB).

  In this embodiment, in order to make the sound pressure difference between the sound emitted from the front surface of the speaker SP collected by the microphone M2 and the sound emitted from the communicating portion 4 20 dB or more, the microphone M2 communicates with the front surface of the housing A1. The portion 4 is positioned with the speaker SP interposed therebetween, and the distance X12 between the microphone M2 and the center of the opening 4a of the communication portion 4 is longer than the distance X11 between the microphone M2 and the outer edge of the diaphragm 23 of the speaker SP. The distance X11 is the shortest distance between the microphone M2 and the speaker SP.

Specifically, if the radiated sound from the front surface of the speaker SP and the radiated sound pressure of the radiated sound from the communicating portion 4 are the same at the same distance,
Sound pressure difference = 20 · Log {X12 / X11} ≧ 20 (dB)
Than,
X12 ≧ 10 · X11
Is derived, and the microphone M2, the speaker SP, and the speaker SP are set such that the distance X12 between the microphone M2 and the center of the opening 4a of the communication portion 4 is 10 times or more the distance X11 between the microphone M2 and the outer edge of the diaphragm 23 of the speaker SP. If the communication part 4 is arrange | positioned, a sound pressure difference will be 20 dB or more, and the cancellation amount reduction of the speaker sound by the communication part 4 can be suppressed.

  FIG. 15 shows the frequency characteristics of the sound collected by the microphone M2, the characteristic Y3 is the radiated sound from the front surface of the speaker SP, and the characteristic Y4a is the radiated sound from the communicating portion 4 when X12 ≧ 10 · X11. The characteristic Y4b represents the sound radiated from the communicating portion 4 when X12≈X11. The characteristic Y5 indicates the sum of the radiated sound from the front surface of the speaker SP collected by the microphone M2 and the radiated sound from the communication unit 4 when X12≈X11.

  First, when X12≈X11, a frequency region in which the sound pressure difference between the sound radiated from the front surface of the speaker SP (characteristic Y3) collected by the microphone M2 and the sound radiated from the communicating portion 4 (characteristic Y4b) is 20 dB or more. Zb is a region having a frequency fb or higher. Therefore, by providing the communication part 4, compared with the case where the sealed housing is used (FIG. 16 shows the frequency characteristics of the sound collected by the microphone M2 when the sealed housing is used). Although the lower limit frequency that can be output by the speaker SP is expanded, the lower limit frequency that can secure the amount of cancellation of the speaker sound becomes high, and a sufficient howling prevention effect cannot be expected in a low frequency region.

  On the other hand, when X12 ≧ 10 · X11, which is the configuration of the present embodiment, the radiated sound (characteristic Y4a) collected from the communication unit 4 collected by the microphone M2 is sound pressure from the characteristic Y4b when X12≈X11. The frequency region Za in which the level is reduced by about 20 dB and the sound pressure difference between the sound emitted from the front surface of the speaker SP collected by the microphone M2 (characteristic Y3) and the sound emitted from the communication unit 4 (characteristic Y4a) is 20 dB or more is The lower limit frequency at which the amount of cancellation can be secured is expanded toward the low frequency side compared to the case where the frequency fa (<fb) or higher and X12≈X11. Therefore, the expansion of the lower limit frequency at which the speaker SP can be output by the communication unit 4 and the expansion of the lower limit frequency by which the cancellation amount of the speaker sound can be ensured by the signal processing unit 10e are compatible.

  Further, as shown by a broken line in FIG. 1, by arranging a sound absorbing material 40 such as a nonwoven fabric in the communication part 4, sound waves (especially high frequency bands) other than the frequency band enhanced by the communication part 4 are absorbed. The adverse effect on the amount of cancellation of the speaker sound caused by the sound wave radiated from the communication unit 4 can be reduced.

  In addition, as shown in FIG. 17, the communication portion 4 may be formed in a cylindrical shape having an opening 4a formed in the side surface of the housing A1, and both ends opened from the opening 4a into the rear air chamber Br. The position of the communication part 4 is not particularly limited as long as the position satisfies the relationship of X12 ≧ 10 · X11.

  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.

(Embodiment 2)
In the first embodiment, the call module MJ is housed in the apparatus main body A2. However, in this embodiment, as shown in FIGS. 18 and 19, the housing A1 of the call module MJ is used as the apparatus main body. By providing the call switch SW1 in A1, the apparatus main body A2 having another configuration shown in the first to fourth embodiments is unnecessary.

  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. (A) (b) It is a figure which shows the frequency characteristic of the radiated sound pressure in front of the speaker SP. It is a figure which shows the relationship between the sound pressure difference of the radiated sound from a speaker front, and the radiated sound from a communicating part, and the cancellation amount of a speaker sound. It is a figure which shows the frequency characteristic of the sound collected with the 2nd microphone. It is a figure which shows the frequency characteristic of the sound collected with the 2nd microphone when the sealed housing is used. It is side surface sectional drawing which shows another structure of a communication apparatus. It is side surface sectional drawing which shows the structure of the communication apparatus of Embodiment 2. It is a perspective view which shows a structure same as the above.

Explanation of symbols

A Communication device MJ Communication module A1 Housing SP Speaker MB1 Microphone board M1, M2 Microphone Bf Front air chamber Br Rear air chamber 4 Communication unit 4a Opening portion 10 Audio processing unit

Claims (4)

A housing;
A speaker attached to the housing and outputting audio information from one side to the outside of the housing;
A rear air chamber that is a space formed on the other side of the speaker in the housing;
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;
A communication device comprising: a communicating portion that allows the rear air chamber and the outside of the housing to continue through an opening provided in the housing.   2. The communication apparatus according to claim 1, wherein the first microphone is disposed so that a sound collection surface faces the diaphragm of the speaker.   The communication device according to claim 1 or 2, wherein a distance between the second microphone and the opening is set to be 10 times or more a shortest distance between the second microphone and the diaphragm of the speaker.   The call device according to any one of claims 1 to 3, wherein a sound absorbing material is disposed in the communication portion.

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