JP2009055483A - Intercom device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an intercom device capable of preventing hauling without reducing the cancel amount of speaker sounds, by suppressing divided vibration of a diaphragm of a speaker. <P>SOLUTION: The intercom device comprises: a speaker SP which is mounted on a housing A1 and outputs sound information from one surface side to the outside of the housing A1; a rear air chamber Br that is a space formed at another surface side of the speaker SP within the housing A1; a microphone M1 which collects sounds and outputs a sound signal; a microphone M2 which is disposed at a position distant from the speaker SP rather than the microphone M1, collects sounds and outputs a sound signal; a sound processing unit 10 which transfers the sound signal of the microphone M2 after canceling the sound signal of the microphone M1 therefrom; and a sound tube 40 that is a pressure increasing means for increasing pressure within the rear air chamber Br at a predetermined frequency at which a diaphragm 23 of the speaker SP generates divided vibration. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a call device.

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

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

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

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

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

  The entire diaphragm of a speaker normally vibrates with the same phase. However, when a sound wave to be radiated has a certain frequency, it generates a divided vibration in which a plurality of vibration regions having different phases are generated.

  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 reasons, and its purpose is to suppress the divided vibration of the diaphragm of the speaker and to prevent howling without reducing the amount of cancellation of the speaker sound. To provide an apparatus.

  According to the first aspect of the present invention, a speaker that outputs sound information to the outside, a first microphone that collects sound and outputs a sound signal, and a speaker far from the first microphone are disposed, and The second microphone that collects the sound and outputs the sound signal, the sound processing unit that removes the sound signal of the first microphone from the sound signal of the second microphone and transmits the sound signal to the outside, and the diaphragm of the speaker are divided Pressure increasing means for increasing the pressure applied to the diaphragm at a predetermined frequency for generating vibrations.

  According to the present invention, it is possible to prevent howling without suppressing the divided vibration of the diaphragm of the speaker and reducing the amount of cancellation of the speaker sound by the sound processing unit.

  According to a second aspect of the present invention, the pressure increasing means according to the first aspect further comprises a rear air chamber that is a space formed on the second surface side of the speaker to output audio information from the one surface side of the speaker to the outside. Increases the pressure in the rear air chamber at the predetermined frequency.

  According to the present invention, the vibration of the diaphragm is suppressed by adding the stiffness of the air in the air chamber after the internal pressure is increased to the stiffness of the speaker at a predetermined frequency at which the diaphragm of the speaker generates the divided vibration. Howling can be prevented without reducing the amount of cancellation of speaker sound by the sound processing unit.

  According to a third aspect of the present invention, the pressure increasing means according to the first aspect of the present invention further comprises a front air chamber that is a space formed on the first surface side of the speaker to output audio information from one surface side of the speaker to the outside. Increases the pressure in the front air chamber at the predetermined frequency.

  According to the present invention, the divided vibration of the diaphragm is suppressed by adding the stiffness of the air in the front air chamber to the stiffness of the speaker at a predetermined frequency at which the diaphragm of the speaker generates divided vibration, and the speaker by the sound processing unit Howling can be prevented without reducing the amount of sound cancellation.

  According to a fourth aspect of the present invention, in the second or third aspect, the pressure increasing means is formed in a hollow shape having one end opened and the other end closed, and communicated with the rear air chamber or the front air chamber through the opening. The tube is configured to have a length based on an odd multiple of 1/2 of the wavelength of the predetermined frequency.

  According to the present invention, due to the action of the acoustic tube, the internal pressure of the rear air chamber or the front air chamber with respect to a sound wave of a predetermined frequency is increased, and the divided vibration of the diaphragm is suppressed.

  According to a fifth aspect of the present invention, in the second or third aspect, the pressure increasing means is formed in a hollow shape having one end opened and the other end closed, and communicates with the rear air chamber or the front air chamber through the opening. An acoustic tube having a length based on an odd multiple of 1/4 of the wavelength of the frequency that improves the sound pressure emitted from the speaker is provided, and the predetermined frequency is a mechanical impedance of air in the rear air chamber or the front air chamber And the acoustic impedance of the acoustic tube are included in a frequency band where the mechanical system impedance is maximized.

  According to the present invention, due to the action of the acoustic tube, the internal pressure of the rear air chamber or the front air chamber with respect to a sound wave of a predetermined frequency is increased, and the divided vibration of the diaphragm is suppressed.

  A sixth aspect of the present invention is the method according to the second or third aspect, wherein the pressure increasing means sets the frequency at which the sound pressure radiated from the speaker is reduced by a standing wave generated in the rear air chamber or the front air chamber to the predetermined frequency. It is characterized by being set to.

  According to the present invention, due to the action of the standing wave, the internal pressure of the rear air chamber or the front air chamber with respect to the sound wave having a predetermined frequency is increased, and the divided vibration of the diaphragm is suppressed.

  As described above, according to the present invention, there is an effect that howling can be prevented without suppressing the divided vibration of the diaphragm of the speaker and reducing the amount of cancellation of the speaker sound.

  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. 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. 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 wires W (see FIG. 2). 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. A rear air chamber Br, which is a space surrounded by the speaker SP and the back surface side of the speaker SP (the yoke 20 side), is formed, and the front air chamber Bf passes through the sound hole 12 of the housing A1 and the sound hole 60 of the apparatus main body A2. It communicates with the outside. The rear air chamber Br becomes a space that is insulated (not communicated) with the front air chamber Bf because the end portion of the support 21 of the speaker SP and the inner surface of the housing A1 are in close contact with each other. Furthermore, when the body A10 of the housing A1 and the cover A11 are in close contact with each other, the rear air chamber Br becomes a space insulated from the outside air. That is, the rear air chamber Br is sealed and insulated from other 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, 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 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. 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. 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 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. 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, the level adjustment corresponding to the difference (X2−X1) in the distance between the two microphones M1, M2 and the speaker SP is performed to match the output levels of the two microphones M1, M2 with respect to the sound from the speaker SP (FIG. 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 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. 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. 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 fs is obtained. In the vicinity, as shown in the amplitude velocity distributions of FIGS. 11A and 11B, the phase inversion phases Za are formed on the boundary of the phase inversion axis Za formed in the diameter direction substantially along the fixing direction of the speaker wiring W. Two vibration regions G1 and G2 are generated in the diaphragm 23. 10 and 11A 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. 12). 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 fo1 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 parts. The frequency fs at which the vibration is generated is expressed by [Equation 2]. The lowest resonance frequency fo1 is the ideal characteristic that is the same as that of the speaker SP alone.

FIG. 13 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 500 to 600 Hz of the lowest resonance frequency fo1. The frequency fs at which the split vibration of the two splits is generated is set to 800 to 900 Hz. The frequency f1 with respect to the lowest resonance frequency fo in FIG. 13 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 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. 14A to 14C show characteristics in a state where the gain and delay time of the signal processing unit 10e are adjusted so that the amount of cancellation of the speaker sound becomes substantially zero at 2 KHz and is affected by the divided vibration. The signals Y14 and -Y23 (inverted signals of Y23) input to the adder circuit 35 have a sound pressure level difference (FIG. 14A) and a phase difference (FIG. 14) near the frequency fs (800 to 900 Hz). 14 (b)) greatly fluctuates, and the amount of cancellation of the speaker sound in the signal Ya output from the adder circuit 35 (FIG. 14 (c)) is reduced to the minimum level near the frequency fs, which adversely affects howling prevention. Giving.

  Therefore, in this embodiment, the influence of the divided vibration is suppressed by increasing the internal pressure of the rear air chamber Br of the housing A1. Specifically, as shown in FIGS. 1 and 3, along the inner wall surface of the body A10 surrounding the rear air chamber Br on the rear surface of the speaker SP, one end is separated from the inner wall surface and the other end is continued to the inner wall surface. The tube wall 41 is erected, and 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. Is arranged. 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.

  When an odd multiple of ½ of the wavelength of the sound wave incident on the acoustic tube 40 is substantially equal to the total length Lp1 of the acoustic tube 40, as shown in FIG. 15 (showing the case of ½ wavelength), the sound pressure Pa Is the maximum at the opening end 40a (at this time, the particle velocity Va becomes 0), and the total length is set to an odd multiple of ½ wavelength of the frequency fs (hereinafter referred to as ½ wavelength). (Referred to as acoustic tube 401) is provided in the rear air chamber Br of the housing A1, and the inside of the half-wave acoustic tube 401 communicates with the rear air chamber Br via the open end 40a. Compared to the case without the tube 401, the internal pressure of the rear air chamber Br with respect to the sound wave having the frequency fs increases. That is, the half-wavelength acoustic tube 401 acting as described above constitutes pressure increasing means for increasing the pressure in the rear air chamber Br at the frequency fs at which the diaphragm 23 generates divided vibration, and the frequency fs. Then, the stiffness of the air in the rear air chamber Br provided with the half-wave acoustic tube 401 is added to the stiffness of the speaker SP. However, considering the correction of the open end of the ½ wavelength acoustic tube 401, the total length of the ½ wavelength acoustic tube 401 is set to an odd multiple of approximately ½ of the wavelength of the frequency fs.

  Accordingly, when the internal pressure of the rear chamber Br increases with respect to the sound wave having the frequency fs, the divided vibration of the diaphragm 23 is suppressed, and the phase difference between the sound waves radiated from the regions G1 and G2 is reduced. As shown in FIG. 16, the amplitude velocity distribution is close to a piston motion in which the entire surface of the diaphragm 23 vibrates at the same phase. Then, as shown in FIG. 17, the cancellation amount of the speaker sound in the signal Ya output from the adder circuit 35 does not drop at the frequency fs as compared with FIG. The amount of cancellation of speaker sound is secured to prevent howling. That is, howling can be prevented without suppressing the divided vibration of the diaphragm 23 of the speaker SP and reducing the amount of cancellation of the speaker sound.

(Embodiment 2)
The communication device A of the present embodiment uses an acoustic tube 40 (hereinafter referred to as a quarter-wave acoustic tube 402) whose overall length is set to an odd multiple of 1/4 of the wavelength of the frequency fs at which split vibration occurs. Different from the first embodiment. However, considering the opening end correction of the ¼ wavelength acoustic tube 402, the total length of the ¼ wavelength acoustic tube 402 is set to an odd multiple of approximately ¼ of the wavelength of the frequency fs.

  The ¼ wavelength acoustic tube 402 is a speaker at the resonance frequency fr by utilizing the fact that the input impedance becomes extremely small at the resonance frequency fr of the closed tube (frequency at which the total length of the tube coincides with an odd multiple of approximately ¼ wavelength). The sound pressure of the SP output is increased to improve the sound quality. When a sound wave having the resonance frequency fr is incident, the reflected wave becomes a waveform whose phase is inverted with respect to the incident wave, and the incident wave and the reflected wave cancel each other. Thus, the sound wave propagating from the opening end 40a to the outside is reduced.

  A quarter-wave acoustic tube 402 having a resonance frequency fr≈800 Hz is provided in the housing A1 with respect to the frequency fs (800 to 900 Hz) at which split vibration of two parts is generated. By communicating with the rear air chamber Br through the open end 40a, the radiated sound pressure characteristic when the quarter-wave acoustic tube 402 is provided increases in frequency from a low frequency region as shown in FIG. As the sound pressure level increases, the sound pressure level becomes maximum at 800 Hz near the resonance frequency fr, but in the frequency band D1 of 800 to 1000 Hz, the sound pressure level decreases as the frequency increases, and then increases again. That is, the sound pressure level is lowered in the frequency band D1 of 800 to 1000 Hz after the sound pressure level is maximized in the vicinity of 800 Hz due to the action of the ¼ wavelength acoustic tube 402.

Here, the mechanical equivalent circuit of the vibration model including the quarter-wave acoustic tube 402 generates a force Fs that vibrates the diaphragm 23 at the diaphragm speed Vs (m / s) as shown in FIG. A vibration source F1 is provided, and mechanical electrical impedance Zme (= Ze / G ² ), diaphragm impedance Zs (= Zms + Za), and rear air chamber impedance Zr (rear) are provided between both ends of the vibration source F1. A parallel circuit of a stiffness Sr of air in the air chamber Br and an impedance Zp of the acoustic tube 40 (hereinafter referred to as acoustic impedance Zp) is connected in series. Ze is a voice coil impedance, G is a force coefficient at the time of conversion from electric energy to mechanical energy, Zms is a mechanical impedance of diaphragm 23 [mechanical resistance of diaphragm 23, weight of diaphragm 23 and voice coil 25, and speaker. Series of stiffness with SP edges and the like], Za is a radiation impedance [series circuit of mechanical resistance of air in the rear air chamber Br and air added mass].

  As shown in FIG. 20, the mechanical system impedance Z2 (= Zp + Zr) obtained by synthesizing the acoustic impedance Zp and the rear air chamber impedance Zr is minimum at the frequency fo3 (≈fr), and each mechanical system impedance is the housing A1. When the quarter-wave acoustic tube 402 is provided, the mechanical system synthetic impedance Z1a (= Zs + Zr + Zp) is lower than the mechanical system impedance Z1b (= Zs + Zr) when the quarter-wave acoustic tube 402 is not provided in the housing A1. The sound pressure is improved in the vicinity.

  Further, the lowest resonance frequency of the speaker SP when the quarter wavelength acoustic tube 402 is provided in the housing A1 is fo3, the lowest resonance frequency fo1 of the speaker SP alone, and the quarter wavelength acoustic tube 402 is not provided in the housing A1. In the case where the lowest resonance frequency fo2 is set, fo1 <fo3 <fo2 is satisfied, and the lowest resonance frequency fo3 when the quarter wavelength acoustic tube 402 is provided is the lowest resonance frequency fo2 when the quarter wavelength acoustic tube 402 is not provided. , And approaches the lowest resonance frequency fo1 of the speaker SP alone. That is, the quarter-wave acoustic tube 402 reduces the minimum resonance frequency when the speaker SP is attached to the housing A1, and the sound quality is improved.

  As described above, the quarter-wave acoustic tube 402 has the lowest resonance frequency fo3 approaching the lowest resonance frequency fo1 of the speaker SP alone, and the mechanical system composite impedance Z2 (= Zp + Zr) at the lowest resonance frequency fo3 is minimized. Thus, the sound pressure and sound quality of the speaker SP attached to the housing A1 are improved.

  However, in the frequency band D1 on the higher frequency side than the lowest resonance frequency fo3, the mechanical system synthetic impedance Z2 rapidly increases and becomes maximum, and the internal pressure of the rear air chamber Br also increases. Therefore, in the present embodiment, by using this, the quarter-wave acoustic tube 402 is formed so that the frequency fs at which the divided vibration of the diaphragm 23 is generated falls within the frequency band D1, and thus the operation as described above. The quarter-wave acoustic tube 402 constitutes pressure increasing means for increasing the pressure in the rear air chamber Br at the frequency fs. At the frequency fs, the quarter-wave acoustic tube 402 is added to the stiffness of the speaker SP. Stiffness of the air in the rear air chamber Br provided is added. Specifically, the resonance frequency fr of the quarter-wave acoustic tube 402 is set to 800 Hz and the frequency band D1 is set to 800 to 1000 Hz with respect to the frequency fs = 800 to 900 Hz at which the divided vibration is generated.

  Therefore, the internal pressure of the rear chamber Br increases with respect to the sound wave of the frequency fs to suppress the divided vibration of the vibration plate 23, the phase difference between the sound waves radiated from the regions G1 and G2 is reduced, and the vibration plate 23 As shown in FIG. 16, the amplitude velocity distribution is close to a piston motion in which the entire surface of the diaphragm 23 vibrates at the same phase. Then, as shown in FIG. 17, the cancellation amount of the speaker sound in the signal Ya output from the adder circuit 35 does not drop at the frequency fs as compared with FIG. The amount of cancellation of speaker sound is secured to prevent howling. That is, howling can be prevented without suppressing the divided vibration of the diaphragm 23 of the speaker SP and reducing the amount of cancellation of the speaker sound.

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

  Moreover, although the acoustic tube 40 (401, 402) of Embodiments 1 and 2 is formed in the rear air chamber Br, as shown in the schematic view of FIG. 21, the acoustic tube 40 protrudes outside the housing A1. May be.

  In addition, the microphone substrate MB1 of the first and second embodiments has both the microphones M1 and M2 mounted on one surface, but the microphone M1 is mounted on one surface of the microphone substrate MB1 as shown in the schematic diagram of FIG. A microphone M2 may be mounted on the surface.

(Embodiment 3)
As shown in the schematic diagram of FIG. 23, the communication device A of the present embodiment is acoustically generated in the front air chamber Bf, which is a space surrounded by the front inner surface of the housing A1 and the surface side of the speaker SP (diaphragm 23 side). The tube 40 (1/2 wavelength acoustic tube 401 or ¼ wavelength acoustic tube 402) is disposed, and the internal pressure of the front air chamber Bf with respect to the sound wave of the frequency fs is increased by the action of the acoustic tube 40, thereby enabling the first embodiment. , 2, the divided vibration of the diaphragm 23 is suppressed, the phase difference between the sound waves radiated from the regions G1 and G2 is reduced, and the amplitude velocity distribution of the diaphragm 23 is as shown in FIG. The entire surface of the plate 23 is close to a piston motion that vibrates at the same phase. Then, as shown in FIG. 17, the cancellation amount of the speaker sound in the signal Ya output from the adder circuit 35 does not drop at the frequency fs as compared with FIG. The amount of speaker sound cancellation is secured to prevent howling. That is, it is possible to prevent howling without suppressing the divided vibration of the diaphragm 23 of the speaker SP and reducing the amount of cancellation of the speaker sound.

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

(Embodiment 4)
In the first to third embodiments, the acoustic tube 40 (1/2 wavelength acoustic tube 401 or ¼ wavelength acoustic tube 402) increases the internal pressure of the front air chamber Bf or the rear air chamber Br of the housing A1, and the diaphragm 23 However, the communication device A of the present embodiment reduces the internal pressure of the rear air chamber Br by the action of standing waves generated by sound waves radiated from the back surface of the diaphragm 23 to the rear air chamber Br. It raises and the divided vibration of the diaphragm 23 is suppressed.

  The frequency of the standing wave generated in the rear air chamber Br is determined by the capacity, shape, etc. of the rear air chamber Br, and the internal pressure of the rear air chamber Br becomes higher at the frequency of the standing wave.

  Therefore, by setting the capacity, shape, etc. of the rear air chamber Br so that the frequency of the standing wave becomes the frequency fs at which the divided vibration of the diaphragm 23 is generated, the frequency 23 at which the diaphragm 23 generates the divided vibration is set. A pressure increasing means for increasing the pressure in the rear air chamber Br is configured, and at the frequency fs, the stiffness of the air in the rear air chamber Br where the standing wave is generated is added to the stiffness of the speaker SP.

  Therefore, the internal pressure of the rear chamber Br increases with respect to the sound wave of the frequency fs to suppress the divided vibration of the vibration plate 23, the phase difference between the sound waves radiated from the regions G1 and G2 is reduced, and the vibration plate 23 As shown in FIG. 16, the amplitude velocity distribution is close to a piston motion in which the entire surface of the diaphragm 23 vibrates at the same phase. Then, as shown in FIG. 17, the cancellation amount of the speaker sound in the signal Ya output from the adder circuit 35 does not drop at the frequency fs as compared with FIG. The amount of cancellation of speaker sound is secured to prevent howling. That is, howling can be prevented without suppressing the divided vibration of the diaphragm 23 of the speaker SP and reducing the amount of cancellation of the speaker sound.

  Note that the configuration of the communication device A according to the present embodiment is obtained by deleting the acoustic tube 40 from FIG. 1, and the other configurations are the same as those of the other embodiments, so that the description thereof is 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 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 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. (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 operation | movement of a 1/2 wavelength acoustic tube same as the above. It is a top view which shows a motion of the diaphragm at the time of raising an internal pressure same as the above. It is a figure which shows the cancellation amount at the time of raising an internal pressure same as the above. It is a figure which shows the sound pressure level at the time of providing the quarter wavelength acoustic tube of Embodiment 2. FIG. It is a figure which shows a mechanical equivalent circuit when there exists an acoustic tube same as the above. It is a figure which shows the frequency characteristic of mechanical system impedance same as the above. It is the schematic which shows another form of an acoustic tube same as the above. It is the schematic which shows another form of a microphone substrate same as the above. FIG. 6 is a schematic diagram illustrating a configuration of a third embodiment.

Explanation of symbols

A Caller MJ Caller module A1 Housing M1, M2 Microphone SP Speaker 23 Diaphragm Br Rear air chamber 10 Audio processing unit 40 Acoustic tube

Claims (6)

A speaker that outputs audio information to the outside;
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;
And a pressure increasing means for increasing the pressure applied to the diaphragm at a predetermined frequency at which the diaphragm of the speaker generates divided vibrations.   Audio information is output from one side of the speaker to the outside, and a rear air chamber that is a space formed on the other side of the speaker is provided, and the pressure increasing means controls the pressure in the rear air chamber at the predetermined frequency. The communication device according to claim 1, wherein the communication device is increased.   Voice information is output from one side of the speaker to the outside, and includes a front air chamber that is a space formed on one side of the speaker, and the pressure increasing means controls the pressure in the front air chamber at the predetermined frequency. The communication device according to claim 1, wherein the communication device is increased.   The pressure increasing means is formed in a hollow having one end opened and the other end closed, and an acoustic tube communicating with the rear air chamber or the front air chamber through the opening is connected to an odd number ½ of the wavelength of the predetermined frequency. 4. The call device according to claim 2, wherein the call device is configured to have a length based on a double.   The pressure increasing means is formed in a hollow shape having one end opened and the other end closed, communicates with the rear air chamber or the front air chamber through the opening, and has a wavelength of 1 that improves the sound pressure radiated from the speaker. / 4 having an acoustic tube set to a length based on an odd multiple of / 4, and the predetermined frequency is a mechanical impedance obtained by synthesizing the mechanical impedance of the air in the rear air chamber or the front air chamber and the acoustic impedance of the acoustic tube. 4. The communication device according to claim 2, wherein the communication device is included in a maximum frequency band.   The pressure increasing means is configured to set a frequency at which a sound pressure radiated from a speaker is reduced by a standing wave generated in the rear air chamber or the front air chamber to the predetermined frequency. 2. The communication device according to 2 or 3.

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