JP2006080590

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DESCRIPTION JP2006080590
An object of the present invention is to cause variations in directivity and an audio output level
because the characteristics of an audio signal input to a directivity synthesis circuit differ
depending on the level difference and frequency characteristics of a microphone unit. SOLUTION:
An n band dividing circuit for dividing an audio signal outputted from n microphone units into m
bands for each microphone unit and an audio signal divided into bands become n internal
references M audio level comparison circuits comparing audio signal levels of audio signals in
the same band divided from audio signals output from one microphone unit, and level differences
of audio signals output from the audio level comparison circuit An audio level control circuit for
controlling the level of the audio signal output from the band division circuit based on the above,
and n band synthesis circuits for synthesizing the band-divided audio signals output from the
audio level control circuit And a directivity synthesis circuit that generates directivity from the
outputs of the n band synthesis circuits. [Selected figure] Figure 1
Audio signal processing device
[0001]
The present invention relates to an audio recording apparatus incorporated in a video camera, a
voice recorder, and the like.
[0002]
In recent years, for example, in microphones used for video cameras, a microphone device that
generates directivity characteristics using a plurality of microphone units is used (see, for
example, Patent Document 1).
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[0003]
Hereinafter, a conventional microphone device will be described with reference to the drawings.
[0004]
FIG. 4 is a diagram showing the configuration of the embodiment of the conventional
microphone device.
The units 61, 62 and 63, which are all nondirectional microphone units, are arranged on the
same straight line so that the distance between the units 61 and 62 and the distance between the
units 62 and 63 are d. .
The cutoff frequency of the high pass filter 64 is f1, the cutoff frequency of the high pass filter
65 is f2, and f1 is set to a frequency higher than f2.
A high pass filter 64 is used to remove low frequency components of the output signal of the unit
61.
[0005]
Also, the low frequency component of the output signal of the unit 62 is removed using the high
pass filter 65, and the output signal of the high pass filter 65 is subjected to a phase shift delay
according to the unit interval d using the phase shifter 68, and then subtracted. Is subtracted
from the output signal of the high pass filter 64 using the filter 70. The output signal of the
subtractor 70 is nondirectional in the frequency band lower than f1 and becomes primary sound
pressure gradient type unidirectionality in the frequency band higher than f1. Similarly, using the
unit 62, the unit 63, the high pass filter 66 whose cutoff frequency is f1, the high pass filter 67
whose cutoff frequency is f2, the phase shifter 69, and the subtractor 71 In the directivity, in a
band of f1 or more, a signal having a primary sound pressure gradient type unidirectivity is
obtained.
[0006]
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Furthermore, after removing low frequency components of the output signal of the subtractor 70
using the high pass filter 12, the difference signal between the output signal of the high pass
filter 72 and the output signal of the subtractor 71 is taken using the subtractor 73, A
microphone is obtained which has no directivity in the frequency band below f1 and a secondary
sound pressure gradient type single directivity in the frequency band above f1. UnexaminedJapanese-Patent No. 5-145986
[0007]
However, in the above-described conventional configuration, the characteristics of the audio
signal input to the directivity synthesis circuit are different depending on the level difference of
the audio signal output from the microphone unit and the frequency characteristic of the
microphone unit. It has the problem of causing variations in levels.
[0008]
In order to solve the above problems, the audio signal processing device according to the present
invention comprises, for each microphone unit, the first to nth microphone units and the audio
signal outputted from the microphone unit, which are arranged at intervals. An audio signal for
each same band divided from an audio signal output from one microphone unit serving as the n
internal reference as an n band division circuit for dividing into m bands and an audio signal
subjected to band division And m audio level comparison circuits for comparing audio signal
levels with each other, and an audio level for controlling the level of the audio signal output from
the band division circuit based on the level difference of the audio signals output from the audio
level comparison circuit A control circuit, n band synthesis circuits for synthesizing band-divided
audio signals outputted from the audio level control circuit, and the n band synthesis circuits And
a directivity synthesis circuit for generating a directivity from the output of the circuit.
[0009]
According to the present invention, the directivity and the audio output level can be obtained
even when the characteristics of the audio signal input to the directivity synthesis circuit differ
depending on the level difference of the audio signal output from the microphone unit and the
frequency characteristic of the microphone unit. It has the advantage of not causing variations.
[0010]
The invention according to claim 1 of the present invention is characterized in that the first to
nth (where n is an integer of 2 or more) microphones spaced apart from one another, and the
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audio signals output from the microphones for each microphone n band dividing circuits for
dividing into m (m is an integer of 2 or more) frequency bands, and one of the n microphones as
a reference microphone for comparing audio signal levels, and output from this reference
microphone Audio signal obtained by dividing the audio signal into m frequency bands, and
audio signal obtained by dividing an audio signal output from a microphone other than the
reference microphone into m (m is an integer of 2 or more) frequency bands, An audio level
comparison circuit that compares audio signal levels for each same frequency band, and the band
division circuit outputs the signal based on the level difference of the audio signal output from
the audio level comparison circuit. Audio level control circuit for controlling the audio signal
level of the audio signal to be reproduced, n band synthesis circuits for synthesizing the banddivided audio signals output from the audio level control circuit, and the n band synthesis circuits
It has a directivity synthesis circuit that generates k (k is an integer of 1 or more) single
directivity or the like from the output of the circuit.
[0011]
Thus, a band division circuit that divides the directivity of an audio signal produced by the
directivity synthesis circuit and the purpose of preventing variations in output signal from being
divided into a plurality of frequency bands and an audio signal for comparing the level difference
of each audio signal Audio level control circuit for controlling the level of the audio signal output
from the band division circuit based on the level difference between the level comparison circuit
and the audio signal output from the audio level comparison circuit; This is realized by using a
band synthesis circuit that synthesizes voice signals that are band-divided and a directivity
synthesis circuit that generates directivity from the output of the band synthesis circuit.
[0012]
Embodiment 1 FIG. 1 is a diagram showing an embodiment of an audio signal processing
apparatus according to the present invention.
[0013]
As shown in FIG. 1, 1 and 2 are microphone units, and in this embodiment, non-directional
microphones are used.
3 and 4 are input n audio signals output from the microphone units 1 and 2 (n is an integer of 2
or more).
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In this embodiment, the frequency band division circuit (hereinafter referred to as a band
division circuit), which is m band division means for dividing into n = 2) frequency bands, the
number of division is 4 in this embodiment. It is not limited to this.
Audio level comparison means 5 to 8 are audio level comparison means for comparing audio
signal levels with audio signals in the same band divided from an audio signal output from one of
the n microphone units serving as a reference. Although the number of audio level comparison
circuits is four in this embodiment, the number of audio level comparison circuits is not limited
to this.
An audio level control circuit 9-12 is an audio level control means for controlling the level of the
audio signal output from the band division circuit 3 based on the level difference of the audio
signals output from the audio level comparison circuits 5-8. Although four voice level control
circuits are provided in the present embodiment, the number of voice level control circuits is not
limited to four.
13 and 14 are band synthesizing circuits which are band synthesizing means for synthesizing
band-divided audio signals outputted from the audio level control circuits 9 to 12, and 15 is k
from the outputs of the band synthesizing circuits 13 and 14 (k is A directivity synthesis circuit
which is directivity synthesis means for generating one or more integers of directivity (for
example, a single directivity of stereo, etc.), 16 and 17 are output terminals for outputting an
audio signal from the directivity synthesis circuit 15 In this configuration, two output terminals
are provided because of stereo output, but the number is not limited to this number.
[0014]
With respect to the audio signal processing apparatus including the above-described
components, the relationship and operation of each component will be described using the
drawings.
[0015]
The microphone units 1 and 2 are nondirectional microphone units, respectively.
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The outputs of the respective microphone units 1 and 2 are input to the band dividing circuits 3
and 4.
[0016]
The band dividing circuits 3 and 4 are constituted by circuits as shown in FIG. 2, for example. In
the figure, reference numerals 21 to 29 denote delay units, 30 to 38 denote multipliers, and 2a
denotes an audio signal input terminal 2b to 2e. Is an output terminal of the band-divided audio
signal.
The audio signal input from 2a passes through this band division circuit, and the middle and low
levels output from the output terminals of the low-range audio signals 301 and 2c output from
the output terminal 2b as shown in FIG. Audio signals 302 and 3d output from the output
terminals of 2d, and an audio output signal divided into four bands such as the high frequency
audio signal 304 output from the output terminals of 2e be able to.
[0017]
In the case of the circuit shown in FIG. 1, an audio signal input to the microphone unit 2 and
output from the band division circuit 4 is used as a reference signal, and a signal output from the
band division circuit 3 is the same frequency band as an audio signal to be compared. The audio
level comparison circuits 5 to 8 compare the audio signal levels each time.
[0018]
The audio level control circuits 9 to 12 control the level of the audio signal output from the band
division circuit 4 based on the level difference of the audio signals output from the audio level
comparison circuits 5 to 8 to obtain a band division circuit. It becomes possible to match the
audio signal of each frequency band output from 4 with the audio signal level of each frequency
band output from the band dividing circuit 3.
[0019]
The audio signals whose voice signal levels have been adjusted for each frequency band are
synthesized with frequency bands by the band synthesis circuits 13 and 14, and are input to the
directivity synthesis circuit 15.
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[0020]
In the directivity synthesis circuit 15, based on the audio signals output from the frequency band
synthesis circuits 13 and 14, for example, the audio signal is converted into an audio signal
having stereo directivity characteristics with unidirectivity.
[0021]
As a result, when the voice input to the directivity synthesis circuit 15 has a difference in level or
frequency characteristics of the audio signal level, the directivity generated by the directivity
synthesis circuit 15 can not be sufficiently obtained. In the case of the embodiment, sufficient
directivity characteristics are obtained by frequency-dividing the input speech signal, comparing
the speech levels, and matching the frequency characteristics of the speech signal input to the
directivity synthesis circuit 15. Is possible.
[0022]
In the present embodiment, the case where two microphone units are used is described, but three
or more microphone units may be used.
The combination of the characteristics at that time is optional.
[0023]
Although the frequency band division in the frequency band dividing circuits 3 and 4 is divided
into four frequency bands, the divided bands may be divided into three or more than five
frequency bands.
[0024]
Also, although the stereo characteristics are described with respect to the directional
characteristics generated, other characteristics may be used.
[0025]
The audio signal processing device of the present invention is useful as an audio signal collection
device such as a video camera.
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The present invention can be applied to an apparatus that generates directivity with a plurality of
microphones, such as a digital still camera and a voice recorder, as well as a video camera.
[0026]
A block diagram of an audio signal processing apparatus showing an embodiment of the present
invention A block diagram showing an example of a band division circuit used for an audio signal
processing apparatus according to an embodiment of the present invention A characteristic
showing an image of frequency band division in the embodiment Block diagram of conventional
directivity synthesis circuit
Explanation of sign
[0027]
1, 2 microphone units 3, 4 frequency band dividing circuits 5, 6, 7, 8 voice level comparison
circuits 9, 10, 11, 12 voice level control circuits 13, 14 frequency band synthesis circuits 15
directivity synthesis circuits 16, 17 voices Output terminal
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