JP4893644B2 - 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 particular, when an acoustic tube is provided in the rear chamber, which is the space on the back side of the speaker, in order to improve the output characteristics of the speaker, the direction of the phase reversal axis of the divided vibration generated in the diaphragm is caused by the action of the acoustic tube. Determined.

  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 its purpose is to reduce the amount of cancellation of speaker sound even when a speaker diaphragm provided with an acoustic tube in a rear air chamber is in a divided vibration. And providing a communication device capable of preventing howling.

  The invention according to claim 1 is a speaker that is attached to the housing and outputs sound from one side of the diaphragm to the outside of the housing, a first microphone that collects sound and outputs a sound signal, and a speaker. A second microphone arranged at a position farther than the first microphone and collecting the voice and outputting the voice signal; and the voice signal of the first microphone is removed from the voice signal of the second microphone and transmitted to the outside. An audio processing unit, a rear air chamber that is a space in the housing formed on the other surface side of the speaker, and an acoustic tube that is formed in a hollow having at least one end opened and communicated with the rear air chamber through the opening. The first and second microphones are arranged in parallel along a linear direction substantially orthogonal to a straight line connecting the opening of the acoustic tube in the rear air chamber and the center of the speaker diaphragm.

  According to the present invention, the first and second microphones are arranged side by side along a linear direction orthogonal to a straight line connecting the opening of the acoustic tube in the rear air chamber and the center of the diaphragm of the speaker. The phase inversion axis of the divided vibration and the microphone arrangement direction are in the same direction, and the influence of the divided vibration can be minimized to ensure the maximum amount of cancellation of the speaker sound. That is, howling can be prevented without reducing the amount of cancellation of speaker sound even when the speaker diaphragm provided with an acoustic tube in the rear air chamber is in divided vibration.

  The invention of claim 2 is characterized in that, in claim 1, the housing is formed in a rectangular box shape having a long side portion and a short side portion, and an opening of the acoustic tube is provided in the long side portion of the housing. To do.

  According to this invention, by providing the opening of the acoustic tube in the long side portion of the housing, the microphone is disposed in the substantially longitudinal direction of the housing, and the microphone can be separated from the outer surface of the side wall of the housing. The volume of speaker sound reflected from the outer surface of the side wall can be reduced, and the amount of cancellation of speaker sound can be prevented from deteriorating.

  The invention of claim 3 is characterized in that, in claim 2, an opening of the acoustic tube is provided at a position where a perpendicular from the center of the diaphragm of the speaker intersects at the long side portion of the housing.

  According to the present invention, the microphone can be separated as much as possible from the outer surface of the side wall of the housing, and deterioration of the amount of cancellation of speaker sound can be further prevented.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the acoustic tube is formed by opening one end and closing the other end.

  According to this invention, the volume of the speaker can be secured with a smaller acoustic tube.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the rear air chamber is spatially insulated from the outside of the housing.

  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 sixth aspect of the present invention, in any one of the first to fifth 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 seventh aspect of the present invention, in any one of the first to sixth aspects, the first and second microphones are arranged on the same substrate on which the 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.

  The invention according to claim 8 is the sound collection surface of the second microphone according to claim 7, wherein the substrate is attached to the outer surface of the housing, the sound collection surface of the first microphone faces the diaphragm of the speaker. Is arranged toward the outside of 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, in the present invention, howling can be prevented without reducing the amount of cancellation of speaker sound even when the speaker diaphragm provided with an acoustic tube in the rear air chamber is in divided vibration. There is an effect.

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

(Embodiment)
The call device A of this embodiment is shown in FIGS. 1 and 2, 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. 4, the audio processing unit 10 is configured by 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. 2, 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 wires W (see FIG. 1). The speaker wire W has one end on the voice coil 25 side along the back surface of the circular diaphragm 23. The other end side is fixed to the amplifying unit 10d of the sound processing unit 10 by being fixed with resin in the radial direction.

  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 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, the microphone substrate MB1 is configured such that a microphone M1 and a microphone M2 made of a capacitor type silicon microphone are mounted on one surface of the module substrate 2 on which a wiring pattern is formed, and can be attached to the outer surface of the housing A1. In the present embodiment, one surface of the module substrate 2 is disposed 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. The sound collection surface of the microphone M1 faces the diaphragm 23 of the speaker SP toward the front air chamber Bf, and can reliably collect the sound from the speaker SP. The microphone M2 is fitted into a recess 14 provided on the front surface of the housing A1, and the sound collecting surface of the microphone M2 is a sound collecting hole 2a formed on the module substrate 2 and a sound formed on the front surface of the apparatus main body A2. Since it faces the outside (front) of the communication device A through the hole 61, it is possible to reliably collect the voice from the speaker located in front of the communication device A. That is, the sound emitted by the speaker SP and the sound emitted by the speaker are separated and collected by the microphones M1 and M2. Further, since both the microphones M1 and M2 are mounted on the one surface 2a of the module substrate 2, the thickness of the microphone substrate MB1 can be reduced.

  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.

  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 sound collecting holes of the microphones M1 and M2 are X1 and X2, respectively, X1 <X2. In this embodiment, the microphones M1 and M2 pick up the sound output of the speaker SP. In order to prevent howling that occurs, the following configuration is provided.

  First, as shown in FIG. 5, 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 (400 to 3000 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 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.

  6 to 9 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 sound collecting holes 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. 6A and 6B).

  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. 7 ( 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. 8A and 8B).

  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. 9A to 9C). 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 oriented in the same direction, 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. 4) 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. This split vibration is generated at a frequency fs (theoretically fs = 2fo) where the radiated sound wave is slightly higher than the lowest resonance frequency fo of the speaker SP, as shown in the amplitude velocity distributions of FIGS. Two vibration regions G1 and G2 having opposite phases with respect to the phase inversion axis Za are generated in the vibration plate 23. 10 and 11A are perspective views as seen from the surface side of the diaphragm 23. FIG.

  FIG. 12 shows sound pressure characteristics when the speaker SP is attached to a standard baffle defined in JIS C5532, and in this embodiment, the range of the lowest resonance frequency fo is 500 to 600 Hz, and divided vibration is generated. The range of the frequency fs is 800 to 900 Hz. If the standard baffle defined in the JIS C5532 is used, it is possible to measure the lowest resonance frequency equivalent to the case where the speaker SP is attached to a baffle plate having an infinite size (ideal baffle plate). Furthermore, it can be said that the lowest resonance frequency fo measured in this way is the same ideal characteristic as that of the speaker SP alone. In this embodiment, the standard baffle defined in JIS C5532 is used. However, even if the standard sealed box defined in JIS C5532 is used, a baffle plate having an infinite size (ideal baffle) is used. The lowest resonance frequency equivalent to the case where the speaker SP is attached to the plate) can be measured.

  Next, the influence of the divided vibration of the diaphragm 23 on the speaker sound canceling process will be described.

  The diaphragm 23 at the time of divided vibration splits and vibrates in two vibration areas G1 and G2 with the phase inversion axis Za as a boundary. In FIG. 11, the vibration area G1 is displaced in the + direction and the vibration area G2 is displaced in the-direction. In addition, an initial phase difference is generated between the sound waves radiated from the two vibration regions G1 and G2, and an acoustic direction is generated between the vibration regions G1 and G2 and the microphones M1 and M2. 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. 13A to 13C show characteristics under the influence of the divided vibration after adjusting the gain and delay time of the signal processing unit 10e so that the cancellation amount of the speaker sound becomes substantially zero at 2 KHz. The signals Y14 and -Y23 (inverted signals of Y23) input to the adder circuit 35 have a sound pressure level difference (FIG. 13A) and a phase difference (FIG. 13) near the frequency fs (800 to 900 Hz). 13 (b)) greatly fluctuates, and the amount of cancellation of the speaker sound (FIG. 13 (c)) in the signal Ya output from the adder circuit 35 is reduced to the minimum level near the frequency fs, which adversely affects howling prevention. Giving.

  The influence of this divided vibration on the amount of cancellation of speaker sound by the signal processing unit 10e depends on the angle α between the phase inversion axis Za and the arrangement direction Zb of the microphones M1 and M2 shown in FIG. As shown in FIG. 15, when the phase inversion axis Za and the microphone placement direction Zb are orthogonal to each other (angle α = 90 °), the amount of cancellation of speaker sound with respect to the angle α is most affected by the divided vibration. When the phase inversion axis Za and the microphone arrangement direction Zb are in the same direction (angle α = 0 °), the cancellation amount is maximized without being affected by the divided vibration. Therefore, in order to minimize the influence of the divided vibration and ensure the maximum amount of speaker sound cancellation by the signal processing unit 10e, the phase inversion axis Za and the microphone arrangement direction Zb may be set in the same direction. I understand that.

  In the present embodiment, the acoustic tube 40 is provided in the rear air chamber Br, and the direction of the phase inversion axis Za is determined by the acoustic tube 40. As shown in FIGS. 1 to 3, the acoustic tube 40 has one end separated from the inner wall surface along the inner wall surface of the body A10 surrounding the rear air chamber Br on the back surface of the speaker SP and the other end continuous to the inner wall surface. A hollow acoustic tube 40 is formed by the tube wall 41, the inner wall surface of the body A10, and the back surface of the cover A11. The acoustic tube 40 is a small-capacity rear chamber Br. Is placed inside. The acoustic tube 40 is a hollow closed tube that is bent along the inner wall surface of the rear air chamber Br and has a rectangular cross-sectional shape formed around the rear air chamber Br, and has one end opened (open end 40a). The other end is closed (closed end 40b), and the inside of the pipe communicates with the rear air chamber Br via 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. 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.

  Then, by setting the overall length of the acoustic tube 40 to approximately ¼ wavelength of the frequency (in this embodiment, a low frequency in the vicinity of 700 to 800 Hz) at which the sound pressure level from the speaker SP is desired to be increased, Since the resonance frequency shifts to a lower frequency side and the sound pressure level of the speaker SP increases, the sound quality and efficiency of the speaker SP are improved even if the rear air chamber Br has a small capacity. In addition, the acoustic tube 40 is not configured to have both ends opened, but can be configured to have a configuration in which one end is opened and the other end is closed, so that the volume of the speaker SP can be secured with a smaller acoustic tube.

  By providing such an acoustic tube 40 in the rear air chamber Br, when the capacity of the rear air chamber Br is small, the rear air chamber Br also acts as a kind of acoustic tube, as shown in FIG. The positions of the open end 40a and the closed end 40b of the acoustic tube 40 are different from those in FIG. 3), and the traveling direction Zc of the sound wave generated between the open end 40a of the acoustic tube 40 and the center of the diaphragm 23 of the speaker SP. A sound pressure node Zd is generated. Then, before and after the node Zd of the sound pressure with respect to the traveling direction Zc of the sound wave, vibration regions G1 and G2 in which the sound wave phases are reversed are generated. In FIG. 16, the node Zd of the sound pressure passes through the center of the diaphragm 23, but there are cases where it passes through other than the center of the diaphragm 23.

  When a sound wave in the vicinity of the frequency fs at which the divided vibration is generated is output from the speaker SP and a sound pressure node Zd is generated in the vicinity of the diaphragm 23, the direction in which the phase inversion axis Za of the divided vibration is generated is the sound pressure node. The direction coincides with Zd. This is because the sound wave traveling direction Zc is approximately the direction in which the sound pressure distribution is generated, and the sound pressure is minimized in the vicinity of the sound pressure node Zd orthogonal to the sound wave traveling direction Zc in the vicinity of the diaphragm 23. On both sides of the node Zd (that is, on both sides of the phase inversion axis Za), vibration regions G1 and G2 in which the phases of the sound waves are opposite to each other are generated. That is, the direction of the phase reversal axis Za of the divided vibration is determined by the position of the opening end 40a of the acoustic tube 40 in the rear air chamber Br (the phase reversal can be achieved even if the rotational direction position of the diaphragm 23 of the speaker SP is adjusted). The direction of the axis Za does not change).

  Therefore, in the communication device A, the traveling direction of sound waves generated between the opening end 40a of the acoustic tube 40 and the center of the diaphragm 23 of the speaker SP (the opening end 40a of the acoustic tube 40 and the center of the diaphragm 23 of the speaker SP). By setting each arrangement so that Zc and the arrangement direction Zb of the microphones M1 and M2 are orthogonal to each other, the phase inversion axis Za and the microphone arrangement direction Zb become the same direction, and the divided vibration It is possible to minimize the influence and to secure the maximum amount of speaker sound cancellation by the signal processing unit 10e. In FIG. 16, the microphone M1 is disposed so as to face a portion deviated from the center of the diaphragm 23. However, even with such an arrangement, the speaker sound canceling effect by the signal processing unit 10e can be obtained.

  Here, if each arrangement is set so that the traveling direction Zc of the sound wave and the arranging direction Zb of the microphones M1 and M2 are orthogonal to each other (Zc and Zb intersect at 90 °), of course, the above effect can be obtained. However, the above effect can be obtained even if each arrangement is set so that the traveling direction Zc of the sound wave and the arrangement direction Zb of the microphones M1 and M2 intersect each other at approximately 90 ° without being exactly orthogonal to each other. . That is, the microphones M1 and M2 may be arranged in the vicinity of the phase inversion axis Za along a linear direction orthogonal to the sound wave traveling direction Zc.

  As shown in FIG. 17, the body A10 of the housing A1 is formed in a rectangular shape having four sides (side walls) composed of a long side portion A10a and a short side portion A10b. If the opening end 40a of the acoustic tube 40 is provided, the traveling direction Zc of the sound wave is formed in a substantially short direction of the body A10 (housing A1), and the arrangement direction Zb of the microphones M1 and M2 is the body A10 (housing A1). The microphones M1 and M2 (particularly the microphone M2) can be separated from the outer surface of the side wall of the housing A1, and the amount of speaker sound reflected from the outer surface of the side wall can be reduced. It is possible to prevent deterioration in the amount of cancellation of speaker sound by the unit 10e.

  Furthermore, in FIG. 17, the opening end 40a of the acoustic tube 40 is provided at a position where the perpendicular from the center of the diaphragm 23 of the speaker SP intersects in the long side portion A10a of the body A10, and the traveling direction Zc of the sound wave is the body A10. (Housing A1) is formed in the short direction, microphones M1 and M2 are disposed in the longitudinal direction of body A10 (housing A1), and microphones M1 and M2 (especially microphone M2) are arranged on the side wall of housing A1. It is possible to separate from the outer surface as much as possible, the amount of the speaker sound reflected from the outer surface of the side wall can be further reduced, and the amount of cancellation of the speaker sound by the signal processing unit 10e can be further prevented.

  On the other hand, as shown in FIG. 18, if the opening end 40a of the acoustic tube 40 is provided in the short side portion A10b of the body A10, the sound wave traveling direction Zc is formed in the longitudinal direction of the body A10 (housing A1), and the microphone M1. , M2 is formed in a substantially short direction of the body A10 (housing A1), and the microphones M1 and M2 (particularly the microphone M2) cannot be separated from the outer surface of the side wall of the housing A1, and are reflected from the outer surface of the side wall. It becomes easy to collect the speaker sound that causes the signal processing unit 10e to degrade the amount of cancellation of the speaker sound.

  Further, by attaching the microphone board MB1 on which the microphones M1 and M2 are mounted on the module board 2 to the outer surface of the housing A1, the microphones M1 and M2 can be positioned with respect to the phase inversion axis Za efficiently and accurately. The amount of cancellation of speaker sound by the signal processing unit 10e is stabilized.

  The microphone substrate MB1 of the present embodiment has both the microphones M1 and M2 mounted on one surface, but as shown in the schematic diagram of FIG. 19, the microphone M1 is mounted on one surface of the microphone substrate MB1 and the other surface is mounted. A microphone M2 may be mounted.

(A) (b) It is a perspective view which shows the structure of embodiment. It is side surface sectional drawing which shows the structure of a communication apparatus same as the above. It is a perspective view which shows a part of structure of an acoustic tube 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 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 figure which shows the sound pressure characteristic of the speaker same as the above attached to the baffle board. (A)-(c) It is a figure which shows each characteristic at the time of the divided vibration same as the above. It is a top view which shows the arrangement | positioning direction of a phase inversion axis | shaft and a microphone same as the above. It is a figure which shows the change of the cancellation amount by the phase inversion axis | shaft same as the above, and the arrangement | positioning direction of a microphone. It is a perspective view which shows one form of the arrangement | positioning direction of a phase inversion axis | shaft same as the above and a microphone. It is a perspective view which shows another form of the arrangement | positioning direction of a phase inversion axis | shaft same as the above and a microphone. It is a perspective view which shows another form of the arrangement | positioning direction of a phase inversion axis | shaft same as the above and a microphone. It is the schematic which shows another form of a microphone substrate same as the above.

Explanation of symbols

A Calling device MJ Calling module A1 Housing M1, M2 Microphone SP Speaker 23 Diaphragm 40 Acoustic tube 40a Open end 40b Closed end

Claims (8)

A speaker attached to the housing and outputting sound from one side of the diaphragm to the outside of 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 rear chamber which is a space in the housing formed on the other surface side of the speaker;
It is formed in a hollow having at least one end opened, and includes an acoustic tube communicating with the rear air chamber through the opening,
The first and second microphones are arranged side by side along a linear direction substantially orthogonal to a straight line connecting the opening of the acoustic tube in the rear air chamber and the center of the diaphragm of the speaker.   2. The communication device according to claim 1, wherein the housing is formed in a rectangular box shape having a long side portion and a short side portion, and an opening of the acoustic tube is provided in the long side portion of the housing.   3. The communication device according to claim 2, wherein an opening of the acoustic tube is provided at a position where a perpendicular from the center of the diaphragm of the speaker intersects in the long side portion of the housing.   4. The communication device according to claim 1, wherein the acoustic tube is formed by opening one end and closing the other end.   5. The communication device according to claim 1, wherein the rear air chamber is spatially insulated from the outside of the housing.   6. The communication device according to claim 1, wherein a sound collection surface of the first microphone faces a diaphragm of the speaker.   7. 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 substrate is attached to the outer surface of the housing, the sound collecting surface of the first microphone is opposed to the diaphragm of the speaker, and the sound collecting surface of the second microphone is disposed toward the outside of the housing. The call device according to claim 7.

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