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JPH09289539

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DESCRIPTION JPH09289539
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
noise reduction type handset in which a differential type microphone for blocking ambient noise
is accommodated in a transmitter.
[0002]
2. Description of the Related Art An example of this type of noise reduction type handset is
disclosed in Japanese Patent Application Laid-Open No. 62-203453. The transmitter section of
the noise reduction type handset proposed here is a first piezoelectric diaphragm to which a
speech voice coming from the transmitter port of the transmitter section is input, and the back
side of the first piezoelectric diaphragm Is housed in a differential type microphone having the
first piezoelectric diaphragm and a second piezoelectric diaphragm disposed in the opposite
direction, and the first piezoelectric diaphragm and the second piezoelectric diaphragm are in
reverse phase. In the state of being connected in series to the circuit, it is connected to the
telephone circuit side (not shown). In addition, in the transmission part accommodating the
differential type microphone, a vent hole for introducing ambient noise into the second
piezoelectric diaphragm is bored.
[0003]
In such a configuration, when the second piezoelectric diaphragm is vibrated by the sound
pressure due to the ambient noise entering from the back side of the transmitter, the first
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piezoelectric diaphragm is oscillated due to the call voice and the ambient noise. Among the
output signals, those due to ambient noise are electrically offset, and only the call signal by the
call voice is taken out as an output to improve the call quality.
[0004]
SUMMARY OF THE INVENTION In the differential microphone of the above-described
conventional noise reduction type handset, the front air chamber is provided on the front surface
of the first piezoelectric diaphragm, and the second piezoelectric diaphragm is different. A front
air chamber is provided on the back of the second piezoelectric diaphragm in order to introduce
ambient noise from the back side of the dynamic microphone to vibrate the second piezoelectric
diaphragm.
With these two front air chambers, as shown in FIG. 6, the output characteristic e in the
transmission sensitivity-frequency characteristic causes resonance at a specific frequency "F",
and the transmission output A sharply increases. Because of this, transmission sensitivity in other
frequency bands is lowered and call quality is significantly lowered. In order to prevent this,
there are methods of changing the structure of the whole handset or correcting with the
characteristics of the microphone, but in the case of the former, it is necessary to prepare a
handset of various structures, and in the case of the latter. In order to correct the characteristics,
it is necessary to change the circuit configuration, all of which are time-consuming and expensive
to develop.
[0005]
Accordingly, the present invention has been made in view of the above-described conventional
problems, and an object of the present invention is to provide a noise reduction type handset in
which the quality of calls is improved by a simple configuration.
[0006]
SUMMARY OF THE INVENTION In order to achieve this object, the noise reduction type handset
according to the present invention comprises a first piezoelectric diaphragm to which a speech
voice is input and a second to which ambient noise is input. And a sound transmission unit
containing a differential type microphone including the piezoelectric vibration plate of the
second aspect, wherein a vent hole for inputting ambient noise is formed in the second
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piezoelectric vibration plate. A space for noise reduction is formed between the second
piezoelectric diaphragm and the vent, and resonance means is provided for resonating with a
vibration wave of a specific frequency among vibration waves generated in the space for noise
reduction. It is
Therefore, the transmission power can be prevented from increasing by shifting the phases of
specific frequencies whose transmission power is increased by the resonance means and
canceling out each other. Further, in the noise preventing type handset according to the present
invention, the space for noise preventing and the space on the receiving part side are separated
by the resonance means. Therefore, the specific vibration wave generated in the noise protection
space does not leak from the noise protection space. Further, in the noise reduction type handset
according to the present invention, the resonance means is formed by a plurality of resonance
spaces. Therefore, the vibration wave of a specific frequency generated in the noise protection
space resonates uniformly by the resonance means. Further, the noise reduction type handset
according to the present invention is provided with a resonance space which resonates with a
frequency different from a specific frequency. Therefore, the resonance means corresponds to
the spread of the width at a specific frequency.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to the drawings. Fig. 1 is an exploded perspective view showing
the main part of the noise reduction type handset according to the present invention, Fig. 2 (a) is
a plan view of the same with the upper case removed, and Fig. 1 (b) is a IIb-IIb line in (a). 3 is a
model of a waveform showing the relationship between the phase and wavelength of the
oscillating wave of frequency "F", and FIG. 4 shows the transmission sensitivity-frequency
characteristic of the noise reduction type handset according to the present invention. FIG.
[0008]
In these figures, what is generally indicated by a reference numeral 1 is a noise preventing type
handset, which is provided with a lower case 2 and an upper case 3 which form a casing of the
handset. Reference numeral 4 denotes a transmitter formed in a concave shape at one end of the
lower case 2, 5 a transmitter formed in a slit on the bottom of the transmitter 4, and 6 an
elongated hole on the side of the transmitter. It is a vent hole drilled in the
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[0009]
A ring-shaped holder 7 is provided with a large diameter recess 8 at the center and a small
diameter hole 9 bored in the center of the recess 8. The holder 7 is fixed to the bottom of the
transmitter 4 with an adhesive so as to correspond to the mouthpiece 5 of the second
embodiment. Reference numeral 10 denotes a differential type microphone, in which first and
second piezoelectric diaphragms (not shown) are incorporated in the same manner as the noise
preventing type transmitter disclosed in the above-mentioned JP-A-62-203453. The two
piezoelectric diaphragms are connected in the reverse phase to the communication circuit side
and fixed in the recess 8 of the holder 7.
[0010]
Reference numeral 12 denotes a flat rectangular parallelepiped resonator, which is provided with
twelve resonance spaces 13 formed in a T-shaped cross section and arranged in a matrix, and the
flange portion 14 is protruded at the lower part of the circumferential side It is set up. The
resonance spaces 13 resonate with the vibration wave a (refer to FIG. 3) of the frequency “F”
among the vibration waves generated in the noise prevention space 15 described later, and the
resonance is out of phase with the vibration wave a The vibration wave b is output. The flange
portion 14 of the resonator 12 is fixed to the upper end 4 a of the transmitting portion 4 so as to
separate the space of the transmitting portion 4 and the space 16 on the receiving portion side,
thereby making the difference between the resonator 12 and the difference. A space 15 for noise
reduction in a sealed state is formed between the dynamic microphone 10 and the same.
[0011]
In such a configuration, when a call is made, the first piezoelectric diaphragm is vibrated by the
speech pressure introduced from the mouthpiece 5 and the sound pressure due to the ambient
noise, and the output signal is transmitted. With respect to the second piezoelectric diaphragm,
sound pressure due to ambient noise is introduced from the vent hole 6 to the back side of the
differential microphone 10, and the first diaphragm is the vibration generated in the second
piezoelectric diaphragm. The opposite output signal is obtained. For this reason, among the
output signals from the first piezoelectric diaphragm, those due to the ambient noise are
electrically offset, whereby only the transmission signal by the call voice is extracted as the
output signal.
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[0012]
At this time, in the noise prevention space 15, as described above in the prior art, as shown in
FIG. 6, the transmission output A in which the transmission sensitivity rapidly increases at a
specific frequency "F" is generated. The vibration wave a of this specific frequency “F” is
output again in the noise prevention space 15 as a resonant vibration wave b which is phase
shifted from the vibration wave a in the resonance space 13 of the resonator 12.
[0013]
As shown in FIG. 3, since the phase of the resonant vibration wave b is shifted with respect to the
vibration wave a of the frequency “F” outputted from the differential microphone 10 to the
noise protection space 15, the resonant vibration wave b Thus, the vibration wave a is attenuated
to generate a vibration wave c. The transmission sensitivity of the vibration wave c is attenuated
more than the transmission output of the vibration wave a as indicated by hatching in the figure,
so that the transmission sensitivity at the frequency "F" is reduced as shown in FIG. For this
reason, the output characteristic d in the transmission sensitivity-frequency characteristic
becomes flat at the maximum output over a wide frequency range, and the average transmission
sensitivity is obtained, whereby the speech quality is improved.
[0014]
As described above, since the communication quality is improved by the resonator 12 regardless
of the structure of the handset, the degree of freedom in design of the handset is increased, and
the structure of the handset 1 is changed as in the prior art, or differential type The design load
is reduced because there is no need to make corrections with the microphone characteristics.
Further, a plurality of resonance spaces 13 of the resonator 12 are arranged in a matrix, and
uniformly cover the entire noise prevention space 15, vibration of a specific frequency “F”
generated in the noise prevention space 15 The speech quality is further improved by uniformly
resonating with the waves. Further, by dividing the noise prevention space 15 in the transmission
section 4 from the noise receiving space 16 by the resonator 12, the vibration wave generated in
the noise prevention space 15 is generated from the noise prevention space 15 Since leakage
does not occur and the characteristics of the vibration wave are stabilized, the resonator 12
functions sufficiently and the speech quality is stabilized.
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[0015]
FIG. 5 is a cross-sectional view showing a second embodiment of the present invention. In the
second embodiment, the height of the resonance space 13 b is formed to be slightly larger than h
with respect to the height h of the resonance space 13 a among the plurality of resonance spaces
13, and resonances of different volumes are generated. Spaces 13a and resonance spaces 13b
are alternately arranged. By this configuration, it is possible to expand the frequency band in
which the resonator 12 resonates, and therefore, it is possible to cope with variations in the
frequency "F" with respect to the output A shown in FIG. Therefore, there is a change in
environmental conditions such as temperature and humidity, and even if the transmission
sensitivity varies, the call quality can be stabilized following this.
[0016]
As described above, according to the present invention, a differential type microphone provided
with a first piezoelectric diaphragm to which speech speech is input and a second piezoelectric
diaphragm to which ambient noise is input Is formed in the second piezoelectric diaphragm to
receive ambient noise, and a noise-proof space is provided between the second piezoelectric
diaphragm and the vent. By providing a resonance means that resonates with the frequency of a
specific vibration wave out of the vibration waves generated in the noise prevention space, the
rapid increase in the transmission power generated at a specific frequency is resonated.
Attenuation can be performed by means, and transmission sensitivity in a wide frequency band is
averaged to improve speech quality. Moreover, regardless of the structure of the handset, the
speech quality is improved by the resonance means, so the degree of freedom in design of the
handset is increased, the structure of the handset is changed as in the prior art, and the
characteristics of the differential microphone are improved. The design load is reduced because
there is no need to make corrections.
[0017]
Further, according to the present invention, the vibration wave does not leak from the noise
preventing space by dividing the noise preventing space from the noise receiving space by the
resonance means. As it is stabilized, the speech quality by the resonance means is stabilized.
[0018]
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Further, according to the present invention, since the resonance means is formed in a plurality of
resonance spaces, it uniformly resonates with the vibration wave generated in the noise
prevention space, so that the communication quality is further improved.
[0019]
Further, according to the present invention, by providing a resonance space that resonates with a
frequency different from a specific frequency, even if variations occur in the frequency of the
oscillatory wave, an oscillatory wave that resonates corresponding to the variation is generated.
The call quality is more stable.
[0020]
Brief description of the drawings
[0021]
FIG. 1 is an exploded perspective view showing an essential part of the noise reduction type
handset according to the present invention.
[0022]
FIG. 2 shows the main part of the noise reduction type handset according to the present
invention, wherein (a) is a plan view showing a state in which the upper case is removed, and (b)
is a sectional view taken along line IIb-IIb in (a).
[0023]
FIG. 3 is a model diagram of a waveform showing the relationship between the wavelength and
the phase of the vibration wave of frequency “F” in the noise reduction type handset according
to the present invention.
[0024]
FIG. 4 is a view showing a transmission sensitivity-frequency characteristic of the noise reduction
type handset according to the present invention.
[0025]
FIG. 5 is a cross-sectional view showing the main part of a second embodiment of the noise
reduction type handset according to the present invention.
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[0026]
FIG. 6 is a diagram showing a transmission sensitivity-frequency characteristic of the
conventional noise reduction type handset.
[0027]
Explanation of sign
[0028]
DESCRIPTION OF SYMBOLS 1 ... noise-proof type handset, 4 ... transmitting part, 5 ... transmitting
port, 6 ... vent hole, 10 ... differential microphone, 12 ... resonator, 13 ... resonance space, 15 ...
space for noise reduction.
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