Communication apparatus
A communication apparatus used for two-way speech wherein the acoustic couplings between a speaker and microphones can be made equal by a simple method, wherein radially arranged microphones are located at equal distances from a speaker, a test signal generation unit outputs a pink noise signal to the speaker, the signal is input to a microphone detecting the sound of the speaker through variable gain amplifiers, attenuated in variable attenuation units, the peak value of absolute values of differences between the signals of an opposing pair of microphones is detected at level detection units, and a level judgment and gain control unit adjusts the gains of the variable gain amplifiers or attenuation amounts of the variable attenuation units so that the value becomes within a sensitivity difference adjustment error.
1. A communication apparatus comprising:
a speaker,
at least one pair of microphones having directivity and arranged on a straight line straddling a center axis of the speaker arranged around the center axis of said speaker radially at equal angles and at equal distances from the speaker,
an amplifying means for independently amplifying sound picked up by the microphones and able to adjust gain,
a level detecting means for calculating an absolute value of a difference of signals of a pair of microphones, among output signals of the amplifying means, and holding a peak value of the calculated absolute values,
a test signal generating means outputting a pink noise signal to the speaker, and
a level judging/gain controlling means adjusting the gain of the amplifying means so that the difference of signals of the pair of microphones detected by the level detecting means becomes within a predetermined sensitivity difference adjustment error when the microphones detect the speaker outputting a sound in accordance with the pink noise.
2. A communication apparatus as set forth in claim 1 , wherein:
the gain of said amplifying means is a gain automatically adjustable digitally by said level judging/gain controlling means,
said level detecting means and said level judging/gain controlling means are integrally configured by a digital signal processor, and
said level judging/gain controlling means digitally changes the gain of said amplifying means.
3. A communication apparatus comprising:
a speaker,
at least one pair of microphones having directivity and arranged on a straight line straddling a center axis of the speaker arranged around the center axis of said speaker radially at equal angles and at equal distances from the speaker,
an amplifying means for amplifying sound picked up by the microphones,
an attenuating means for independently attenuating sound signals amplified by the amplifying means,
a level detecting means for calculating an absolute value of difference of signals of a pair of microphones, among output signals of the attenuating means, and holding a peak value of the calculated absolute values,
a test signal generating means outputting a pink noise signal to the speaker, and
a level judging/gain controlling means adjusting an attenuation amount of the attenuating means so that the difference of signals of the pair of microphones detected by the level detecting means becomes within a predetermined sensitivity difference adjustment error when the microphones detect the speaker outputting a sound in accordance with the pink noise.
4. A communication apparatus as set forth in claim 3 , wherein:
the attenuating means, the level detecting means, and the level judging/gain controlling means are integrally configured by a digital signal processor, and
the attenuation amount of the attenuating means is set digitally by the level judging/gain controlling means.
5. A communication apparatus comprising:
a speaker,
at least one pair of microphones having directivity and arranged on a straight line straddling a center axis of the speaker arranged around the center axis of said speaker radially at equal angles and at equal distances from the speaker,
an amplifying means for independently amplifying sounds picked up by the microphones and able to adjust gain,
an attenuating means for independently attenuating sound signals amplified by the amplifying means,
a level detecting means for calculating an absolute value of a difference of signals of a pair of microphones, among output signals of the attenuating means, and holding a peak value of the calculated absolute values,
a test signal generating means outputting a pink noise signal to the speaker, and
a level judging/gain controlling means adjusting the gain of the amplifying means and/or the attenuation amount of the attenuating means so that the difference of signals of the pair of microphones detected by the level detecting means becomes within a predetermined sensitivity difference adjustment error when the microphones detect the speaker outputting a sound in accordance with the pink noise.
6. A communication apparatus as set forth in claim 5 , wherein:
the attenuating means, the level detecting means, and the level judging/gain controlling means are integrally configured by a digital signal processor, and
the attenuation amount of the attenuating means is set digitally by the level judging/gain controlling means.
7. A communication apparatus as set forth in claim 6 , wherein when the gain of the amplifying means cannot be adjusted digitally,
the level judging/gain controlling means adjusts the attenuation amount of the attenuating means.
8. A communication apparatus as set forth in claim 6 , wherein when the gain of the amplifying means can be adjusted digitally and a control width thereof is smaller than the sensitivity difference adjustment error,
the level judging/gain controlling means adjusts the gain of the amplifying means.
9. A communication apparatus as set forth in claim 6 , wherein when the gain of the amplifying means can be adjusted digitally and the control width thereof is larger than the sensitivity difference adjustment error,
the level judging/gain controlling means adjusts the gain of the amplifying means in a possible range and
then adjusts the attenuation amount of the attenuating means.
10. A communication apparatus as set forth in claim 6 , wherein when the gain of the amplifying means can be adjusted digitally together with the detection signal of a pair of microphones and the control width thereof is smaller than the sensitivity difference adjustment error,
the level judging/gain controlling means
adjusts the gain of the amplifying means for the detection signals of a pair of microphones in the possible range and
then independently adjusts the attenuation amount of the attenuating means.
11. A communication apparatus as set forth in claim 6 , wherein when the gain of the amplifying means can be adjusted digitally together with the detection signal of a pair of microphones and the control width thereof is smaller than the sensitivity difference adjustment error,
the level judging/gain controlling means
independently adjusts the attenuation amount of the attenuating means and
then adjusts the gain of the amplifying means for the detection signals of a pair of microphones in the possible range.
12. A communication apparatus as set forth in claim 6 , wherein when the gain of the amplifying means can be adjusted digitally together with the detection signal of a pair of microphones and the control width thereof is larger than the sensitivity difference adjustment error,
the level judging/gain controlling means
adjusts a higher attenuation amount of the attenuating means between detection signals of the microphones and
then adjusts the gain of the amplifying means for the detection signals of a pair of microphones, and
further adjusts the higher attenuation amount of the attenuating means between the detection signals of the microphones.