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DESCRIPTION JP2009055483

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DESCRIPTION JP2009055483
PROBLEM TO BE SOLVED: To provide a telephone apparatus capable of preventing howling
without suppressing a divided vibration of a diaphragm of a speaker to reduce a cancellation
amount of a speaker sound. SOLUTION: A speaker SP attached to a housing A1 and outputting
audio information from one surface side to the outside of the housing A1, and a rear air chamber
Br which is a space formed on the other surface side of the speaker SP inside the housing A1. A
microphone M1 for collecting voice and outputting a voice signal, a microphone M2 disposed at
a position farther than the microphone M1 with respect to the speaker SP and collecting voice
and outputting a voice signal, and a voice signal of the microphone M2 The sound processing
unit 10 for removing the sound signal of the microphone M1 from the microphone and
transmitting it to the outside, and the sound as pressure increasing means for increasing the
pressure in the rear air chamber 23 at a predetermined frequency at which the diaphragm 23 of
the speaker SP generates divided vibration. And a tube 40. [Selected figure] Figure 1
Intercom
[0001]
The present invention relates to a telephone set.
[0002]
Conventionally, there is a telephone set installed indoors by an intercom system etc., and a
speaker for outputting voice from the telephone set installed at another place, a microphone for
inputting voice to be transmitted to the other telephone set, etc. There is.
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And since howling occurs when the sound generated from the speaker gets into the microphone,
various measures against howling are taken.
[0003]
For example, as a first conventional example, a loop circuit including a speaker and a microphone
is formed in a speech apparatus, and howling occurs when the loop gain exceeds 1, so that loss
in a variable loss circuit provided in the loop circuit By adjusting the amount, there is one that
prevents the howling by setting the loop gain to 1 or less. Here, it is considered that the smaller
one of the transmission signal and the reception signal is not important, and the transmission
loss of the variable loss circuit inserted in the transmission path of the smaller signal level is
increased.
[0004]
However, in the first conventional example, when the distance between the microphone and the
speaker is short, the level of the received voice which is transmitted from the speaker to the
microphone becomes large, the transmission signal becomes larger than the received signal, and
the voice is emitted from the speaker The control circuit is switched to the transmitting state
despite the receiving state, and a state occurs in which the speaker can not emit any sound.
[0005]
Therefore, as a second conventional example, a pair of microphones, a delay circuit for delaying
the output of the microphone closer to the speaker by the delay time of the sound wave
corresponding to the difference between the distance between both the microphones and the
speaker, both microphones and the speaker Level adjustment to match the output level of both
microphones with respect to the sound from the speaker, and the outputs of both microphones
passing through the delay circuit and the level adjustment amplifier circuit. There is a telephone
set in which a differential amplifier circuit is provided and the output of the differential amplifier
circuit is a transmission signal.
[0006]
In this communication device, after the voice from the speaker is picked up by a pair of
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microphones, delay and level adjustment are performed so that the speaker sounds input to both
microphones are offset by the differential amplifier circuit, so only the speaker sound Can be
canceled to prevent howling, and furthermore, transmission voice can be transmitted without
receiving blocking.
(See, for example, Patent Document 1).
Patent No. 2607257 (Page 2 left column line 13 to right column line 3; page 4 right column line
26 to line 49, FIG. 1, FIG. 5)
[0007]
The diaphragm of the speaker usually vibrates with the same phase on the entire surface, but
generates a divided vibration in which a plurality of vibration areas having different phases are
generated when the sound wave to be emitted has a certain frequency.
[0008]
Then, as in Patent Document 1 described above, in the configuration in which the speaker sound
input to both microphones is canceled by the differential amplifier circuit and only the speaker
sound is canceled to prevent howling, the diaphragm is divided during 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 inputted to both microphones
by the differential amplifier circuit, and the howling preventing effect is reduced.
[0009]
The present invention has been made in view of the above circumstances, and an object thereof
is to suppress split vibration of a diaphragm of a speaker and to prevent a howling without
reducing a cancellation amount of the speaker sound. It is in providing an apparatus.
[0010]
According to the first aspect of the present invention, a speaker for outputting voice information
to the outside, a first microphone for collecting voice and outputting a voice signal, and a voice
located at a position farther from the speaker than the first microphone A second microphone
that collects audio and outputs an audio signal, an audio processing unit that removes the audio
signal of the first microphone from the audio signal of the second microphone and transmits the
signal to the outside, and a diaphragm of a speaker And pressure increasing means for increasing
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the pressure applied to the vibrating plate at a predetermined frequency generating the
vibration.
[0011]
According to this invention, 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
by the sound processing unit.
[0012]
The invention according to claim 2 is characterized in that, in claim 1, a rear air chamber which
is a space formed on the other surface side of the speaker by outputting audio information from
the one surface side of the speaker to the outside, the pressure increasing means Is characterized
in that the pressure in the rear air chamber is increased at the predetermined frequency.
[0013]
According to the present invention, at a predetermined frequency at which the diaphragm of the
speaker generates the divided vibration, the stiffness of the air in the air chamber is added to the
stiffness of the speaker after the internal pressure is increased, thereby suppressing the divided
vibration of the diaphragm. Howling can be prevented without reducing the amount of
cancellation of the speaker sound by the audio processing unit.
[0014]
The invention according to claim 3 is characterized in that, in claim 1, a front air chamber which
is a space formed on one side of the speaker by outputting audio information from the one side
of the speaker to the outside, the pressure increasing means Is characterized in that the pressure
in the front air chamber is increased at the predetermined frequency.
[0015]
According to the present invention, the stiffness of the air in the front air chamber is added to the
stiffness of the speaker at a predetermined frequency at which the diaphragm of the speaker
generates the split vibration, whereby the split vibration of the diaphragm is suppressed, and the
speaker by the audio processing unit Howling can be prevented without reducing the amount of
cancellation of sound.
[0016]
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The invention according to claim 4 is characterized in that, in claim 2 or 3, the pressure
increasing means is formed in a hollow that is open at one end and closed at the other end, and is
in acoustic communication with the rear air chamber or the front air chamber via the opening.
The tube is set to have a length based on an odd multiple of 1/2 of the wavelength of the
predetermined frequency.
[0017]
According to the present invention, the internal pressure of the back air chamber or the front air
chamber for the sound wave of the predetermined frequency is increased by the action of the
acoustic tube, and the divided vibration of the diaphragm is suppressed.
[0018]
The invention according to claim 5 is characterized in that, in claim 2 or 3, the pressure
increasing means is formed in a hollow with one end opened and the other end closed, and is
communicated with the rear air chamber or the front air chamber through the opening. The
acoustic tube is set to a length based on an odd multiple of 1⁄4 of the wavelength of the
frequency to improve the radiation sound pressure from the speaker, and the predetermined
frequency is the mechanical impedance of air in the rear air chamber or the front air chamber. It
is characterized in that it is included in a frequency band in which a mechanical system
impedance obtained by combining the above and the acoustic impedance of the acoustic tube is
at a maximum.
[0019]
According to the present invention, the internal pressure of the back air chamber or the front air
chamber for the sound wave of the predetermined frequency is increased by the action of the
acoustic tube, and the divided vibration of the diaphragm is suppressed.
[0020]
According to a sixth aspect of the present invention, in the second or third aspect, the pressure
increasing means may have a frequency at which the sound pressure emitted from the speaker is
reduced by the standing wave generated in the back air chamber or the front air chamber. And is
configured.
[0021]
According to the present invention, due to the action of the standing wave, the internal pressure
of the back air chamber or the front air chamber for the sound wave of the predetermined
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frequency is increased, and the divided vibration of the diaphragm is suppressed.
[0022]
As described above, according to the present invention, it is possible 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.
[0023]
Hereinafter, embodiments of the present invention will be described based on the drawings.
[0024]
(First Embodiment) A call apparatus A according to the present embodiment is shown in FIGS. 1
to 3 and is configured by storing a call module MJ in a rectangular box-shaped apparatus main
body A2 in which the call switch SW1 and the voice processing unit 10 are arranged. Ru.
The apparatus body A2 is formed by joining, for example, two resin molded members, and after
the call switch SW1, the voice processing unit 10, and the call module MJ are accommodated, the
respective joining members are joined by a fitting means or an adhesive or the like. Do.
[0025]
In the call module MJ, a housing A1 having a width of 40 mm × height 30 mm × thickness 8
mm is constituted by a body A10 having an opening in the rear surface and a flat cover A11
covered at the opening of the body A10. , The speaker SP, and the microphone substrate MB1.
A diaphragm 23 described later of the speaker SP is disposed to face a plurality of sound holes
12 formed on the front surface of the housing A1 and a plurality of sound holes 60 formed on
the front surface of the device body A2.
[0026]
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As shown in FIG. 4, the audio processing unit 10 is 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 disposed in the housing A1.
The audio 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 and amplified by
the amplification unit 10d through the audio switch unit 10b, and then the speaker Output from
SP.
In addition, by operating the call switch SW1, it becomes possible to talk, and each voice signal
inputted from the microphone M1 (first microphone) and the microphone M2 (second
microphone) on the microphone substrate MB1 is processed by the signal processing unit 10e.
After signal processing to be described later is performed, the signal 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 through the information line Ls.
That is, it functions as an interphone capable of interactive communication between rooms.
The power supply of the communication device A may be supplied from an outlet provided near
the installation site, or may be supplied via the information line Ls.
[0027]
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 a circular support 21 extends outward from the open
end of the yoke 20.
[0028]
The cylindrical permanent magnet 22 (for example, residual magnetic flux density 1.39T to
1.43T) 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 It is fixed to the end face of 21.
[0029]
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The diaphragm 23 is formed of a thermoplastic plastic (for example, a thickness of 12 μm to 50
μm) such as PET (PolyEthylene Terephtalate) or PEI (Polyetherimide).
A cylindrical bobbin 24 is fixed to the back surface of the diaphragm 23, and is formed by
winding a polyurethane copper wire (for example, φ 0.05 mm) around a kraft paper tube at the
rear end of the bobbin 24. A voice coil 25 is provided.
The bobbin 24 and the voice coil 25 are provided such that the voice coil 25 is positioned at the
open end of the yoke 20, and freely move in the front-rear direction in the vicinity of the open
end of the yoke 20.
[0030]
The voice coil 25 receives an audio signal via a pair of speaker wires W (see FIG. 2), and one end
of the voice wire 25 is along the back of the circular diaphragm 23 on the voice coil 25 side. It is
fixed with resin in the radial direction, and the other end side is connected to the amplification
unit 10 d of the voice processing unit 10.
[0031]
When a voice signal is input to the polyurethane copper wire of the voice coil 25, an
electromagnetic force is generated in the voice coil 25 by the current of the voice signal and the
magnetic field of the permanent magnet 22. It is vibrated in the direction.
At this time, the diaphragm 23 emits a sound according to the audio signal.
That is, a dynamic speaker SP is configured.
[0032]
Then, the outer peripheral end of the circular support 21 of the speaker SP abuts on the inside
front of the housing A1 facing the diaphragm 23, and the speaker SP is fixed with the diaphragm
23 facing the inside front of the housing A1 from the inside Be done.
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[0033]
When the speaker SP is fixed in the housing A1, a front air chamber Bf, which is a space
surrounded by the front inner side of the housing A1 and the front surface side (diaphragm 23
side) of the speaker SP, back inner side and inner side of the housing A1. A rear air chamber Br,
which is a space surrounded by the speaker SP and the back surface side (yoke 20 side) of the
speaker SP, is formed, and the front air chamber Bf is formed via the sound hole 12 of the
housing A1 and the sound hole 60 of the device body A2. It communicates with the outside.
The rear air chamber Br is a space insulated (not in communication) with the front air chamber
Bf as the end of the support 21 of the speaker SP is in close contact with the inner surface of the
housing A1.
Further, the back air chamber Br becomes a space insulated from the outside air by the close
contact of the body A10 of the housing A1 and the cover A11.
That is, the rear air chamber Br is sealed and is insulated from other air pockets.
[0034]
The sound radiated from the back surface of the speaker SP (the back surface of the diaphragm
23) to the back air chamber Br is in phase with the sound radiated from the front surface of the
speaker SP (the front surface of the diaphragm 23) to the front air chamber Bf. (Hereinafter, the
phase of the sound radiated from the front surface of the speaker SP is referred to as the positive
phase, and the phase of the sound radiated from the rear surface of the speaker SP is referred to
as the reverse phase).
However, as described above, since the back air chamber Br is a space having a high degree of
sealing, the sound of the opposite phase radiated from the back surface of the speaker SP to the
back air chamber Br is less likely to leak out of the back air chamber Br. The sound of the
opposite phase leaked from the room Br turns forward and suppresses the decrease in the
radiation pressure by canceling the sound of the positive phase radiated from the surface of the
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speaker SP, and the speaker SP emits the sound to the speaker in front The sound is easy to hear.
[0035]
Further, the other end side of the speaker wire W is led out of the call module MJ through an
insertion hole (not shown) bored in the housing A1, and is connected to the voice processing unit
10 in the device main body A2.
After passing through the speaker wire W, the insertion hole is closed with a resin for sealing the
back air chamber Br.
[0036]
Next, the microphone substrate MB1 mounts the microphone M1 and the microphone M2
formed of a capacitor type silicon microphone on one surface of the module substrate 2 so as to
be attachable to the outer surface of the housing A1.
In the present embodiment, one surface of the module substrate 2 is disposed along the front
outer side of the housing A1, and the microphone M1 is inserted through the opening 13 on the
front surface of the housing A1.
Then, the sound collection surface of the microphone M1 faces the diaphragm 23 of the speaker
SP toward the front air chamber Bf, so that sound from the speaker SP can be reliably collected.
Further, the microphone M2 is fitted in the concave portion 14 provided on the front surface of
the housing A1, and the sound collecting surface of the microphone M2 is a sound collected on
the front surface of the device main body A2 and the sound collecting hole 2a formed on the
module substrate 2 Since it faces the outside (forward) of the communication device A through
the hole 61, it is possible to reliably collect voice from a speaker located in front of the
communication device A.
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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.
[0037]
Furthermore, since the recess 14 housing the microphone M2 is a separated space not
communicating with the rear air chamber Br, the microphone M2 hardly collects the sound
emitted from the speaker SP, and the sound of the speaker SP and the microphone M2 Coupling
is further reduced.
That is, according to 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.
[0038]
When the microphone substrate MB1 is disposed in the housing A1, it is difficult to maintain the
spatial insulation between the front air chamber Bf and the rear air chamber Br, but as in this
embodiment, the microphone substrate MB1 is not used for the housing A1. By attaching to the
outer surface, spatial insulation between the front air chamber Bf and the rear air chamber Br
can be maintained.
[0039]
Then, assuming that distances from the center of the speaker SP to the centers of the
microphones M1 and M2 are X1 and X2, respectively, X1 <X2, and in this embodiment, the
sound output of the speaker SP is picked up by picking up the microphones M1 and M2. The
following configuration is provided to prevent howling.
[0040]
First, as shown in FIG. 5, the signal processing unit 10 e housed in the audio processing unit 10
includes an amplification circuit 30 that non-inverts and amplifies the output of the microphone
M 1, and an audio band (400 to 3000 Hz) from the output of the amplification circuit 30. ), A
delay circuit 32 for delaying the output of the band pass filter 31, an amplification circuit 33 for
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inverting and amplifying the output of the microphone M2, and a voice band from the output of
the amplification circuit 33. A band pass filter 34 for removing noise of frequencies other than
(400 to 3000 Hz) and an adding circuit 35 for adding the outputs of the delay circuit 32 and the
band pass filter 34 are provided.
[0041]
FIGS. 6-9 shows the audio signal waveform of each part of the signal processing part 10 in, when
the sound from a speaker is each sound-collected with the microphones M1 and M2.
First, assuming that 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 delay time of the sound wave corresponding to
the difference (X2-X1) between the two microphones M1 and M2 and the speaker SP is small in
amplitude, and the delay time of the sound wave [Td = (X2-X1) / Cv] (Cv is the speed of sound)
The phase of the output Y21 is delayed (see FIGS. 6A and 6B).
[0042]
The amplifier circuit 30 non-inverts and amplifies the output Y11 to generate an output Y12, and
the amplifier circuit 33 inverts and amplifies the output Y21 to generate an output Y22 whose
phase is inverted by 180 °.
At this time, the level adjustment corresponding to the difference (X2-X1) in the distance
between both the microphones M1 and M2 and the speaker SP is performed to make the output
levels of the two microphones M1 and M2 coincide with the sound from the speaker SP (FIG. a)
see (b)). In the present embodiment, the amplification factor of the amplification circuit 30 is less
than 1, the amplification factor of the amplification circuit 33 is about 1, and the amplification
circuit 33 may be omitted.
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[0043]
Then, the band pass filters 31 and 34 generate outputs Y13 and Y23 obtained by removing noise
of frequencies other than the voice band from the outputs Y12 and Y22 (see FIGS. 8A and 8B).
[0044]
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 to obtain
the output Y14 of the delay circuit 32 and The phase is matched with the output Y23 of the band
pass filter 34 to reduce the noise on the audio signal to be transmitted.
[0045]
The audio component from the speaker SP included in the output Y14 and the audio component
from the speaker SP included in the output Y23 have the same amplitude and the same phase by
the amplification processing and the delay processing, and the adding circuit 35 outputs the
output Y14 and 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, at the output Ya, the sound component from the speaker SP is reduced.
[0046]
Further, 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 with the sound collection surface arranged toward the speaker H The amplitude of
the output Y21 of the microphone M2 is larger than the amplitude of the output Y11 of the
microphone M1 for the voice emitted by the speaker H in front of the microphones M1 and M2
while the amplitude is larger than the amplitude of the output Y21 of 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 becomes larger than the speech component from the speaker H
included in the output Y14. . That is, the amplitude difference between the voice component from
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the speaker H included in the output Y14 and the voice component from the speaker H included
in the output Y23 becomes large, and the output Ya is obtained even if the addition processing is
performed by the adding circuit 35. , The signal corresponding to the speech emitted by the
speaker H remains with sufficient amplitude.
[0047]
As described above, at the output Ya of the addition circuit 35, the voice component from the
speaker SP is reduced, and the voice component emitted from the speaker H ahead of the
communication device A toward the microphone substrate MB1 remains, and at the output Ya
The relative difference between the voice component from the speaker H who wants to leave and
the voice component from the speaker SP that wants to reduce is large. That is, even when the
voice from the speaker H and the voice from the speaker SP are simultaneously generated, only
the voice component from the speaker SP is reduced while maintaining sufficient amplitude for
the voice component from the speaker H. Therefore, it is possible to prevent the howling caused
by the microphones M1 and M2 picking up the audio output of the speaker SP.
[0048]
Further, since the microphone M1 reliably collects the sound emitted by the speaker SP, the
howling prevention processing by the signal processing unit 10e can be reliably performed.
Furthermore, since the microphone M2 has the sound collecting surface and the diaphragm of
the speaker SP facing in the same direction, the acoustic coupling between the speaker SP and
the microphone M2 is reduced, and it becomes difficult for the microphone M2 to collect the
sound emitted by the speaker SP. Thus, the microphone M2 can be disposed 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 miniaturized.
[0049]
Furthermore, since the back air chamber Br is a space with a high degree of sealing, the sound of
the opposite phase radiated from the back surface of the speaker SP to the back air chamber Br
is less likely to leak out of the back 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 phase sound.
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[0050]
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) perform the following processing to
further prevent howling.
[0051]
First, the audio switch unit 10c takes in the output of the audio switch unit 10b as a reference
signal, and performs an operation on the output of the signal processing unit 10e to further
process the audio signal that has looped from the speaker SP into the microphones M1 and M2.
Cancel.
On the other hand, the voice switch unit 10b also takes in 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 causing the voice signal from the speaker to the microphone at the other end of the
callee Cancel the
[0052]
Specifically, the voice switch units 10b and 10c are configured by the speaker SP-microphone
M1, M2-signal processing unit 10e-voice switch unit 10c-communication unit 10a-voice switch
unit 10b-amplifier unit 10d-speaker SP By adjusting the amount of loss in variable loss means
(not shown) provided in the loop circuit, howling is prevented by making the loop gain 1 or less.
Here, it is considered that the smaller one of the transmission signal and the reception signal is
not important, and the transmission loss of the variable loss circuit inserted in the transmission
path of the smaller signal level is increased.
[0053]
Here, if the sound wave to be emitted is lower than a certain frequency, the speaker SP performs
a piston motion in which the entire surface of the diaphragm 23 vibrates in the same phase as
shown in the amplitude velocity distribution of FIG. However, when the sound wave to be emitted
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is equal to or higher than a certain frequency, a plurality of vibration regions having phases
different from each other generate divided vibrations generated in the diaphragm 23. In the
present embodiment, since the speaker wire 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 In the vicinity, as
shown in the amplitude and velocity distributions of FIGS. 11A and 11B, the phases are opposite
to each other with the phase inversion axis Za formed in the diameter direction substantially
along the fixed direction of the speaker wire W as a boundary. Two vibration regions G1 and G2
occur in the diaphragm. 10 and 11A are perspective views of the diaphragm 23 as viewed from
the surface side.
[0054]
The diaphragm 23 of the speaker SP has a circular shape, and the outer peripheral edge is fixed
to the edge of the support 21 (see the schematic view of FIG. 12), and is fixed from the center of
the diaphragm 23 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 of
diaphragm 23 Assuming that 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], 2 The frequency fs at which the divided vibration which is divided is
generated is expressed by [Equation 2]. The lowest resonance frequency fo1 has the same ideal
characteristic as that of the speaker SP alone.
[0055]
[0056]
[0057]
FIG. 13 shows an actual sound pressure characteristic when the speaker SP is attached to a baffle
plate (not shown) having an infinite size, and in the present embodiment, the range of 500 to
600 Hz of the lowest resonance frequency fo1 The frequency fs at which division vibration of
two divisions occurs is set to 800 to 900 Hz.
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Although 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 uneven. The rib is formed, which is
different from the result calculated with the thickness t of the diaphragm 23 being constant as in
the theoretical calculation of the above [Equation 2].
(2) Since the outer peripheral edge portion of the diaphragm 23 is fixed to the support 21 with
an adhesive, the fixed state is not uniform. (3) In order to fix the speaker wiring W on the
diaphragm 23 with resin, the mass of the diaphragm 23 is not uniform. For reasons such as
[0058]
Next, the influence of the divided vibration of the diaphragm 23 on the cancellation process of
the speaker sound will be described.
[0059]
At the time of divided vibration, the diaphragm 23 is divided and vibrated in the two vibration
regions G1 and G2 with the phase inversion axis Za as a boundary, the vibration region G1 is
displaced in the + direction and the vibration region G2 is displaced in the − direction in FIG.
While the sound waves emitted from the two vibration areas G1 and G2 respectively have an
initial phase difference, acoustic directivity is generated between the vibration areas G1 and G2
and the microphones M1 and M2.
Then, an amplitude difference generated in each sound signal emitted from the vibration area G1
and collected by the microphones M1 and M2 and an amplitude difference generated in each
sound signal emitted from the vibration area G2 and collected by the microphones M1 and M2
Are different from each other, and it is difficult to cancel both of the sound waves respectively
emitted from the vibration regions G1 and G2 even if the gain and delay time of the signal
processing unit 10e are adjusted, and the howling prevention effect is reduced. It will
[0060]
FIGS. 14 (a) to 14 (c) show the 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 adding circuit 35 have a sound pressure level difference
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(FIG. 14 (a)) and a phase difference (FIG. 14) in the vicinity of the frequency fs (800 to 900 Hz).
14 (b) greatly fluctuates, and the amount of cancellation of the speaker sound (FIG. 14 (c)) in the
signal Ya output from the adding circuit 35 is reduced to the minimum level around the
frequency fs, adversely affecting howling prevention. It is giving.
[0061]
Therefore, in the present 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, one end is 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 is continued to the inner wall surface. A hollow acoustic pipe
40 is formed by the pipe wall 41, the inner wall surface of the body A10, and the back surface of
the cover A11. The acoustic pipe 40 has a small volume in the rear air chamber Br. Is located in
The acoustic tube 40 is a hollow closed tube having a rectangular cross-sectional shape which is
bent along the inner wall surface of the rear air chamber Br and 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 tube is in communication with the rear air chamber Br via the open end 40a.
[0062]
Then, when an odd multiple of 1/2 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.
Acoustic tube 40 (hereinafter referred to as 1⁄2 wavelength) in which the total length is set to an
odd number multiple of 1⁄2 wavelength of frequency fs. The acoustic tube 401 is provided in the
rear air chamber Br of the housing A1, and the half-wave acoustic tube 401 is communicated
with the rear air chamber Br via the opening end 40a through the open end 40a. Compared with
the case without the pipe 401, the internal pressure of the rear air chamber Br for the sound
wave of the frequency fs increases. That is, the half-wave acoustic pipe 401 acting as described
above constitutes a pressure increasing means for increasing the pressure in the rear air
chamber Br at the frequency fs at which the diaphragm 23 generates the divided vibration. Then,
the stiffness of the air in the air chamber Br after adding the half-wave acoustic tube 401 is
added to the stiffness of the speaker SP. However, in consideration of the aperture end correction
of the half-wave acoustic tube 401, the total length of the half-wave acoustic tube 401 is set to
an odd multiple of about half the wavelength of the frequency fs.
16-04-2019
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[0063]
Therefore, when the internal pressure of the rear air chamber Br increases with respect to the
sound wave of the frequency fs, the divided vibration of the diaphragm 23 is suppressed, and the
phase difference of the sound waves radiated from the regions G1 and G2 decreases. The
amplitude velocity distribution is close to piston movement in which the entire surface of the
diaphragm 23 vibrates in the same phase, as shown in FIG. Then, as shown in FIG. 17, the
amount of cancellation of the speaker sound in the signal Ya output from the adding circuit 35
has no drop at the frequency fs as compared with FIG. Sound volume is secured to prevent
feedback. 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.
[0064]
Second Embodiment The communication device A according to the present embodiment is an
acoustic tube 40 whose total length is set to an odd multiple of 1⁄4 of the wavelength of the
frequency fs at which split vibration occurs (hereinafter referred to as “1⁄4 wavelength acoustic
tube 402”. The second embodiment differs from the first embodiment in that it uses. However,
in consideration of the aperture end correction of the 1⁄4 wavelength acoustic tube 402, the total
length of the 1⁄4 wavelength acoustic tube 402 is set to an odd multiple of about 1⁄4 of the
wavelength of the frequency fs.
[0065]
The quarter-wave acoustic tube 402 uses the fact that the input impedance is extremely small at
the closed tube resonance frequency fr (the frequency at which the total length of the tube
corresponds to an odd multiple of approximately 1⁄4 wavelength). The sound pressure of the SP
output is increased to improve the sound quality. When a sound wave of 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 open end 40 a to the outside is reduced.
[0066]
16-04-2019
19
Then, with respect to the frequency fs (800 to 900 Hz) at which split vibration of two divisions
occurs, the quarter-wave acoustic pipe 402 having a resonance frequency fr ≒ 800 Hz is
provided in the housing A1, By communicating with the rear air chamber Br via the open end
40a, the radiation sound pressure characteristic in the case of including the quarter-wave
acoustic tube 402 is such that the frequency rises from the low frequency range as shown in FIG.
The sound pressure level that has increased as a result 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 rises and then increases again.
That is, after the sound pressure level reaches a maximum around 800 Hz by the action of the
1⁄4 wavelength acoustic pipe 402, the sound pressure level decreases in the frequency band D1
of 800 to 1000 Hz.
[0067]
Here, as shown in FIG. 19, the mechanical equivalent circuit of the vibration model provided with
the 1⁄4 wavelength acoustic pipe 402 generates a force Fs that vibrates the diaphragm 23 at the
diaphragm velocity Vs (m / s). An excitation source F1 is provided, and between both ends of the
excitation source F1, mechanical system electrical impedance Zme (= Ze / G <2>), diaphragm
impedance Zs (= Zms + Za), and rear air chamber impedance Zr A parallel circuit of (the stiffness
Sr of the air in the rear air chamber Br) and the impedance Zp of the acoustic tube 40
(hereinafter referred to as the acoustic impedance Zp) is connected in series. Here, Ze is a voice
coil impedance, G is a force coefficient at the time of conversion from electrical energy to
mechanical energy, Zms is a mechanical impedance of diaphragm 23 [mechanical resistance of
diaphragm 23 and weight of diaphragm 23 and voice coil 25 and speaker Series circuit with
stiffness such as the edge of SP], Za is radiation impedance [series circuit of mechanical
resistance of air in back air chamber Br and air added mass].
[0068]
Then, as shown in FIG. 20, the mechanical system combined impedance Z2 (= Zp + Zr) obtained
by combining the acoustic impedance Zp and the back air chamber impedance Zr becomes
minimum at the frequency fo3 (≒ fr), and the housing A1 The mechanical system synthetic
impedance Z1a (= Zs + Zr + Zp) in the case where the 1⁄4 wavelength acoustic tube 402 is
provided, and the frequency fo3 from the mechanical system synthetic impedance Z1b (= Zs + Zr)
in the case where the 1⁄4 wavelength acoustic pipe 402 is not provided in the housing A1. It
becomes smaller in the vicinity, and the sound pressure is improving.
16-04-2019
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[0069]
Furthermore, the lowest resonance frequency of the speaker SP when the quarter-wave acoustic
tube 402 is provided in the housing A1 is fo3, and the lowest resonance frequency fo1 of the
single speaker SP alone, and the quarter-wave acoustic tube 402 is not in the housing A1. In the
case of the lowest resonance frequency fo2 in the case, fo1 <fo3 <fo2, and the lowest resonance
frequency fo3 in the case where the quarter-wave acoustic tube 402 is provided is the lowest
resonance frequency fo2 in the absence of the quarter-wave acoustic tube 402 , And approaches
the lowest resonance frequency fo1 of the speaker SP alone.
That is, the lowest resonance frequency when the speaker SP is attached to the housing A1 is
lowered by the 1⁄4 wavelength acoustic pipe 402, and the sound quality is improved.
[0070]
As described above, the lowest resonance frequency fo3 approaches the lowest resonance
frequency fo1 of the speaker SP alone by the 1⁄4 wavelength acoustic pipe 402, and the
mechanical system combined impedance Z2 (= Zp + Zr) at the lowest resonance frequency fo3 is
minimized. The sound pressure and sound quality of the speaker SP attached to the housing A1
are improved.
[0071]
However, in the frequency band D1 on the higher frequency side than the lowest resonance
frequency fo3, the mechanical system combined impedance Z2 sharply increases and is
maximized, and the internal pressure of the rear air chamber Br also increases.
Therefore, in the present embodiment, by utilizing this, by forming the 1⁄4 wavelength acoustic
pipe 402 so that the frequency fs at which the divided vibration of the diaphragm 23 is
generated falls within the frequency band D1, the function is performed as described above. The
quarter-wave acoustic tube 402 constitutes a pressure increasing means for increasing the
pressure in the rear air chamber Br at the frequency fs, and at the frequency fs, the quarter-wave
acoustic tube 402 is connected to the stiffness of the speaker SP. After installation, air stiffness in
the air chamber Br is added. Specifically, with respect to the frequency fs = 800 to 900 Hz at
16-04-2019
21
which the divided vibration occurs, the resonance frequency fr of the 1⁄4 wavelength acoustic
tube 402 is set to 800 Hz, and the frequency band D1 is set to 800 to 1000 Hz.
[0072]
Therefore, the internal pressure of the rear air chamber Br increases with respect to the sound
wave of the frequency fs, and the divided vibration of the diaphragm 23 is suppressed, and the
phase difference of the sound waves respectively emitted from the regions G1 and G2 becomes
small. As shown in FIG. 16, the amplitude velocity distribution of the above becomes close to
piston movement in which the entire surface of the diaphragm 23 vibrates in the same phase.
Then, as shown in FIG. 17, the amount of cancellation of the speaker sound in the signal Ya
output from the adding circuit 35 has no drop at the frequency fs as compared with FIG. Sound
volume is secured to prevent feedback. 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.
[0073]
The other configuration is the same as that of the first embodiment and the description is
omitted.
[0074]
The acoustic tubes 40 (401, 402) of Embodiments 1 and 2 are formed in the rear air chamber Br,
but as shown in the schematic view of FIG. 21, the acoustic tube 40 is provided outside the
housing A1. May be
[0075]
Moreover, although microphone board MB1 of Embodiment 1, 2 mounts both microphones M1
and M2 on one side, as shown in the schematic of FIG. 22, microphone M1 is mounted on one
side of microphone board MB1, and others The microphone M2 may be mounted on the surface.
[0076]
(Third Embodiment) As shown in the schematic diagram of FIG. 23, the communication device A
according to the present embodiment is a space surrounded by the front inner side of the
16-04-2019
22
housing A1 and the front surface side (diaphragm 23 side) of the speaker SP. The acoustic pipe
40 (1/2 wave acoustic pipe 401 or 1/4 wave acoustic pipe 402) is disposed in the air room Bf,
and the internal pressure of the front air room Bf for the sound wave of frequency fs is increased
by the action of the acoustic pipe 40 Thus, the divided vibration of the diaphragm 23 is
suppressed as in the first and second embodiments, and 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. As shown, the entire surface of the diaphragm 23 becomes
close to the piston movement oscillating in the same phase.
Then, as shown in FIG. 17, the amount of cancellation of the speaker sound in the signal Ya
output from the adding circuit 35 has no drop at the frequency fs as compared with FIG. Sound
volume is secured to prevent feedback.
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.
[0077]
The other configuration is the same as that of the first or second embodiment, and the
description will be omitted.
[0078]
Fourth Embodiment In the first to third embodiments, the internal pressure of the front air
chamber Bf or the rear air chamber Br of the housing A1 is increased by the acoustic tube 40
(half-wave acoustic tube 401 or quarter-wave acoustic tube 402). Although the divided vibration
of the diaphragm 23 is suppressed, the communication device A according to the present
embodiment has the back air by the action of the standing wave generated by the sound wave
radiated from the back surface of the diaphragm 23 to the back air chamber Br. The internal
pressure of the chamber Br is increased, and the divided vibration of the diaphragm 23 is
suppressed.
[0079]
The frequency of the standing wave generated in the rear air chamber Br is determined by the
capacity, the shape, and the like of the rear air chamber Br, and the internal pressure of the rear
air chamber Br becomes high at the frequency of the standing wave.
16-04-2019
23
[0080]
Therefore, by setting the capacity, shape, and the like 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 occurs, the frequency fs at which the diaphragm 23 generates the divided
vibration The 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 air chamber Br is added to the
stiffness of the speaker SP after generating the standing wave.
[0081]
Therefore, the internal pressure of the rear air chamber Br increases with respect to the sound
wave of the frequency fs, and the divided vibration of the diaphragm 23 is suppressed, and the
phase difference of the sound waves respectively emitted from the regions G1 and G2 becomes
small. As shown in FIG. 16, the amplitude velocity distribution of the above becomes close to
piston movement in which the entire surface of the diaphragm 23 vibrates in the same phase.
Then, as shown in FIG. 17, the amount of cancellation of the speaker sound in the signal Ya
output from the adding circuit 35 has no drop at the frequency fs as compared with FIG. Sound
volume is secured to prevent feedback.
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.
[0082]
The configuration of the communication device A according to the present embodiment is the
one obtained by removing the acoustic tube 40 from FIG. 1, and the other configuration is the
same as that of the other embodiments, and thus the description thereof will be omitted.
[0083]
FIG. 2 is a side cross-sectional view showing the configuration of the communication device of
the first embodiment.
16-04-2019
24
(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 pipe same as the above.
It is a circuit diagram which shows the structure of the audio | voice processing part same as the
above.
It is a circuit block diagram of the 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 movement 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 division | segmentation vibration same as the above. It is a
top view which shows the division | segmentation 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 division |
segmentation vibration same as the above. It is a figure which shows operation | movement of a
1/2 wavelength acoustic pipe same as the above. It is a top view which shows a motion of the
diaphragm at the time of raising the internal pressure same as the above. It is a figure which
shows the cancellation amount at the time of raising the 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 pipe of Embodiment 2. FIG. It is a figure which shows a mechanical system equivalent
circuit in case there exists an acoustic pipe same as the above. It is a figure which shows the
frequency characteristic of a mechanical system impedance same as the above. It is the
schematic which shows another form of an acoustic pipe same as the above. It is the schematic
which shows another form of a microphone board | substrate same as the above. FIG. 7 is a
schematic view showing a configuration of Embodiment 3.
Explanation of sign
[0084]
A Communication device MJ Call module A1 Housing M1, M2 Microphone SP Speaker 23
Diaphragm Br Rear air chamber 10 Audio processing unit 40 Sound tube
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25
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