JPH04318797

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DESCRIPTION JPH04318797
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
microphone device for remote sound collection using a plurality of microphones simultaneously.
[0002]
2. Description of the Related Art An example of the above-mentioned conventional microphone
device will be described below with reference to the drawings. FIG. 2 shows a conventional
microphone device. In FIG. 2, reference numerals 10 to 14 denote first to fifth microphone units,
respectively. Reference numeral 70 denotes a microphone array, which is constituted by the first
microphone unit 10 to the fifth microphone unit 14 linearly arranged. A fan filter 40 receives an
output signal from the microphone array 70 as an input, and filters multiple inputs and one
output. Reference numeral 50 denotes sampling frequency control means for changing the
sampling frequency of the fan filter 40. 60 is an output terminal.
[0003]
The operation of the conventional microphone device configured as described above will be
described below.
[0004]
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First, sound waves arriving at the microphone array 70 are received by the first to fifth
microphone units 10 to 14.
The output signal of the microphone array 70 is subjected to two-dimensional digital filtering by
the fan filter 40. When the observed sound wave signal is considered as two-dimensional data of
sampling in the time direction in the fan filter 40 and sampling in the space direction by the
arrangement of the microphone units 10 to 14, the spectrum of the sound wave has time
frequency f1 and space frequency On the two-dimensional frequency plane represented by f2,
the longitudinal axis direction of the microphone array 70 is 0 °, the incident angle is θ, the
microphone unit interval is d, the sampling frequency is fs, and the sound speed is c, on a
straight line Appear in
[0005]
[Equation 1]
[0006]
On the other hand, the amplitude frequency characteristic of the fan filter 40 is expressed by the
following equation.
[0007]
[Equation 2]
[0008]
At this time, if the amplitude frequency characteristic of the fan filter 40 is an ideal one having a
sufficiently sharp cutoff characteristic represented by (Equation 2), the directivity characteristic
D (θ) of the microphone device is Parameters f1 and f2 of ¦ H (f1, f2) ¦) are converted into θ
according to the relation of (Equation 1) can get.
[0009]
[Equation 3]
[0010]
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The sampling frequency control means 50 changes the sampling frequency fs of the fan filter 40
in the range of c / d <fs.
As a result, the sound collection range shown by (Equation 3) can be changed from a narrow
angle to a wide angle.
[0011]
SUMMARY OF THE INVENTION However, in the above configuration, when constructing a sound
collection system using a plurality of conventional microphone devices simultaneously, a fan
filter which becomes a very expensive digital signal processing device It has a problem that the
cost of the sound collection system becomes too high because a plurality of 40s are required.
[0012]
In view of the above problems, the present invention provides a microphone device with reduced
cost by sharing the fan filter 40 with a plurality of microphone array units.
[0013]
SUMMARY OF THE INVENTION In order to solve the above problems, the microphone device of
the present invention comprises: a first microphone array comprising N microphone units
arranged in a straight line; A second microphone array similar to the first microphone array;
signal combining means for summing and outputting m-th microphone unit outputs of the first
microphone array and the second microphone array; and the signal A fan filter for twodimensional digital filtering the output of the combining means, and a sampling frequency
control means for changing the sampling frequency of the fan filter.
[0014]
According to the present invention, according to the above-described configuration, the fan filter
is applied after the outputs of the first microphone array and the second microphone array are
added.
In the first microphone array, the output signal is represented as two-dimensional data of x1 (m,
n), where m is a spatial sample by the spatial array of microphones and n is a time sample, and
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similarly, the output signal of the second microphone array Assuming that x 2 (m, n) and the fan
filter is assumed to be an FIR type two-dimensional filter, and the filter coefficient is a (k, l), the
output signal y (n) is expressed by the following equation.
[0015]
[Equation 4]
[0016]
According to the addition theorem, the above equation is divided into the first term and the
second term as the following equation.
[0017]
[Equation 5]
[0018]
Equation (5) shows that the first microphone array has a fan filter, and the second microphone
array has a fan filter, and then the result is the same as the configuration of adding. When you
need the conventional microphones of this type, by adding the outputs of the microphone array
first and then applying the fan filter, it is possible to realize the same characteristics as providing
a plurality of conventional microphones with one fan filter Become.
[0019]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A microphone device according to
a first embodiment of the present invention will be described below with reference to the
drawings.
FIG. 1 shows a microphone device according to a first embodiment of the present invention.
[0020]
In FIG. 1, 10 to 14 denote first to fifth microphone units, and 15 denotes a first microphone
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array, in which the first to fifth microphone units 10 to 14 are linearly arranged at equal
intervals. It is configured by arranging.
Reference numerals 20 to 24 denote sixth to tenth microphone units, and reference numeral 25
denotes a second microphone array, in which the sixth microphone units 20 to 10 are linearly
arranged at equal intervals.
[0021]
Reference numeral 30 denotes a first addition means for adding the signals from the first
microphone unit 10 and the sixth microphone unit 20.
Reference numeral 31 denotes second addition means for adding the signals from the second
microphone unit 11 and the seventh microphone unit 21.
Reference numeral 32 denotes third adding means for adding the signals from the third
microphone unit 12 and the eighth microphone unit 22.
A fourth addition means 33 adds the signals from the fourth microphone unit 13 and the ninth
microphone unit 23.
A fifth addition means 34 adds the signals from the fifth microphone unit 14 and the tenth
microphone unit 24.
Reference numeral 35 denotes signal combining means, which comprises first to fifth addition
means 30 to.
A fan filter 40 applies a fan filter to the signal from the signal combining means 35.
Reference numeral 50 denotes sampling frequency changing means for changing the sampling
frequency of the fan filter 40.
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60 is an output terminal.
[0022]
The operation of the microphone apparatus configured as described above will be described
below.
[0023]
FIG. 1 shows the configuration of the first embodiment, and the output signals from the first
microphone array 15 and the second microphone array 25 correspond to the microphone units
corresponding to the signal combining means 35. It is added every time and filtered by the fan
filter 40.
If the above content is expressed by an equation, it becomes (Equation 4). Here, x 1 (m, n) is an
output signal from the first microphone array 15, x 2 (m, n) is an output signal from the second
microphone array 25, and a (k, l) is the fan filter 40. The filter coefficient, m is a spatial sample
parameter, and n is a temporal sample parameter.
[0024]
Equation (4) can be rewritten as equation (5). In Equation (5), the first and second terms
respectively indicate the output of the microphone device according to the conventional
configuration having one fan filter per one microphone array, so in this embodiment, the output
of the microphone device of the conventional example The same effect as when adding and
outputting is obtained.
[0025]
As described above, according to this embodiment, the first microphone array composed of N
microphone units linearly arranged, and the second microphone array similar to the first
microphone array Signal combining means for adding and outputting m-th microphone unit
outputs of the first microphone array and the second microphone array, and a fan filter for twodimensional digital filtering the output of the signal combining means By providing sampling
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frequency control means for changing the sampling frequency of the fan filter, it is possible to
realize a plurality of microphones having directivity characteristics that are variable in the sound
collection range and have no frequency dependency, with one fan filter. The scale can be
reduced.
[0026]
As described above, according to the present invention, there is provided a first microphone
array comprising N microphone units linearly arranged, and a second microphone array similar
to the first microphone array. A signal combining means for summing and outputting m-th
microphone unit outputs of the first microphone array and the second microphone array, and a
fan for performing two-dimensional digital filtering on the output of the signal combining means
By providing a filter and sampling frequency control means for changing the sampling frequency
of the fan filter, it is possible to realize a plurality of microphones having directivity
characteristics that are variable in the sound collection range and have no frequency
dependency, by one fan filter. The circuit scale can be reduced.
[0027]
Brief description of the drawings
[0028]
1 is a microphone device of an embodiment of the present invention.
[0029]
2 is a block diagram of a conventional microphone device.
[0030]
Explanation of sign
[0031]
10 first microphone unit 11 second microphone unit 12 third microphone unit 13 fourth
microphone unit 14 fifth microphone unit 15 first microphone array 20 sixth microphone unit
21 seventh microphone unit 22 Eighth microphone unit 23 ninth microphone unit 24 tenth
microphone unit 25 second microphone array 30 first addition means 31 second 〃 32 third 〃
33 fourth 〃 34 fifth 〃 35 signal Combining means 40 Fan filter 50 Sampling frequency
changing means 60 Output terminal
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