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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultra-high sensitivity sound collecting method and apparatus which is an improvement over the
conventional sound pickup method using a single microphone.
2. Description of the Related Art Conventionally, (1) upsizing of a diaphragm, (2) noise reduction
of a microphone amplifier, and the like have been achieved in order to increase the sensitivity of
a microphone.
However, the high sensitivity achieved by the prior art is at most several dB, which does not
greatly exceed the minimum audible limit of human beings.
The reason is that, since the prior art uses a single microphone, it is basically difficult to
simultaneously achieve high sensitivity and high bandwidth.
Therefore, an object of the present invention is to provide an ultra-high sensitivity sound
collection method and apparatus in which high sensitivity and high band are compatible by
combining a large number of sound collection elements.
[Means for Solving the Problems] In order to achieve the above object, according to the superhigh-sensitivity sound pickup method of the present invention, a plurality of electro-acoustic
conversions each having a sharp resonance characteristic for each specific frequency shifted by a
slight frequency. By using elements and adding the output signals of the respective
electroacoustic transducers in parallel, flat frequency characteristics can be obtained.
Here, in adding the output signals of the electroacoustic transducers in parallel, it is preferable to
add the signals obtained from the band pass filters connected to the subsequent stage of the
respective electroacoustic transducers.
In the super-high-sensitivity sound pickup device according to the present invention, a plurality
of electroacoustic conversion means each having sharp resonance characteristics for each
specific frequency shifted by a slight frequency, and an output signal of the plurality of
electroacoustic conversion means are added. And adding means for obtaining a flat frequency
Here, in addition, it is preferable to connect a band pass filter to the subsequent stage of the
plurality of electroacoustic conversion means.
In the present invention, in order to convert air vibration into an electrical signal with high
sensitivity, by combining a large number of sound pickup elements (microphones) having
different resonance frequencies, it is possible to achieve both high sensitivity and flat frequency
characteristics. It was made possible.
That is, in the present invention, a plurality of electroacoustic transducers having sharp
resonance characteristics are used, and their center frequencies are changed slightly and
Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a system diagram of an ultra-high sensitivity sound pickup apparatus to which the
present invention is applied.
The embodiment shown in the figure includes microphone elements 1 to 30, band pass filters 31
to 60, and an adder 61.
The resonance frequencies of the mechanical systems of the respective microphone elements are
set at 1/3 octave intervals.
Each of the microphone elements 1 to 30 minimally performs resistance control for frequency
characteristic flattening as performed by a normal microphone.
As a result, the outputs 1a-30a of each microphone element have a very high voltage at the
resonant frequency instead of being flat in their frequency characteristics.
The outputs 1a to 30a of the respective microphone elements are passed through the band pass
filters 31 to 60 and then added by the adder 61 to be the final output 62.
The band pass filters 31 to 60 include the resonance frequency of the microphone element in the
pass band thereof, and flatten the frequency characteristic after addition.
The final low output 62 not only has a high voltage, but is flat over a wide band.
In the present embodiment shown in FIG. 1, although 30 microphone elements are used and the
resonance frequency interval is 1⁄3 octave, of course, this numerical value can be arbitrarily
Next, the operation of the present embodiment will be described using FIG. 2 showing the
characteristics of each microphone shown in FIG.
The characteristic of the original electrodynamic microphone is resonance as shown in A.
In an ordinary microphone, an acoustic resistance is provided between the diaphragm and the
rear chamber to suppress resonance, and the frequency characteristic is flattened as shown by
the characteristic B.
However, this results in the sensitivity of the microphone being sacrificed, and the difference
with the noise D added by the preamplifier can not be increased.
On the other hand, in the present embodiment, the acoustic resistance is made as small as
possible, and a band pass filter is inserted in the output to have the characteristic shown in C
In this case, although the frequency band is extremely narrow by itself, a wide band can be
covered by combining a plurality of microphones different in resonance frequency.
FIG. 3 shows that a flat frequency characteristic E can be obtained by combining a plurality of
microphone outputs different in resonance frequency.
According to the present invention, the sensitivity of the microphone can be greatly improved as
compared with the prior art, and the deterioration of the frequency characteristic due to the high
sensitivity can be suppressed.
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