Electrical audio signal processing systems and devices – Feedback suppression
Reexamination Certificate
2003-03-03
2004-01-06
Mei, Xu (Department: 2644)
Electrical audio signal processing systems and devices
Feedback suppression
C381S083000
Reexamination Certificate
active
06674863
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microphone-speaker apparatus, and more particularly to a microphone-speaker apparatus comprising howling sound judging means for judging whether or not a howling sound is produced while a microphone unit is receiving an audio sound outputted by a speaker unit without being affected by an amplitude of the audio sound received by the microphone unit.
2. Description of the Related Art
Up until now, there have been provided a wide variety of microphone-speaker apparatus of this type one typical example of which is shown in FIG.
14
. The conventional microphone-speaker apparatus of this type is disclosed in pages 112-115 of the preprinted version of the Tokyo convention '95 of the Audio Engineering Society, titled “Automatic Finding and Eliminating Feedback System with DSP”.
The conventional microphone-speaker apparatus
20
is shown in
FIG. 14
as comprising a microphone unit
40
for receiving an audio sound represented by a raw sound wave varied in response to a time axis to convert the audio sound to an audio signal, the audio sound being constituted by a plurality of sub-band audio sounds each having an amplitude, the sub-band audio sounds respectively having frequency ranges divided along a frequency axis; audio signal dividing means
50
for dividing the audio signal received from the microphone unit
40
through an input terminal
30
into a plurality of sub-band audio signals respectively indicative of the sub-band audio sounds, each of the sub-band audio signals having a plurality of sequential frames divided along the time axis, and the sequential frames each having a current frame and a preceding frame prior to the current frame; maximum value obtaining means
60
for obtaining the maximum value from among the amplitudes of the sub-band audio signals in each of the sequential frames; and howling sound judging means
70
for judging whether or not the howling sound is produced while the microphone unit
40
is receiving the audio sound outputted by the speaker unit
80
.
The howling sound judging means
70
is operative to judge whether or not the howling sound is produced while the microphone unit
40
is receiving the audio sound outputted by the speaker unit
80
through steps of judging whether or not the maximum value of the amplitudes of the sub-band audio signals in each of the sequential frames exceeds a predetermined threshold value, judging whether or not the frequency range in which the maximum value of the amplitudes of the sub-band audio signals is obtained by the maximum value obtaining means
60
in the current frame is the same as the frequency range in which the maximum value of the amplitudes of the sub-band audio signals is obtained by the maximum value obtaining means
60
in the preceding frame under the condition that each of the maximum value of the amplitudes of the sub-band audio signals obtained by the maximum value obtaining means
60
in the current frame and the maximum value of the amplitudes of the sub-band audio signals obtained by the maximum value obtaining means
60
in the preceding frame exceeds a predetermined threshold value, counting a number of the sequential frame in which the judgment is made that the frequency range in which the maximum value of the amplitudes of the sub-band audio signals is obtained by the maximum value obtaining means
60
in the current frame is the same as the frequency range in which the maximum value of the amplitudes of the sub-band audio signals is obtained by the maximum value obtaining means
60
in the preceding frame under the condition that each of the maximum value of the amplitudes of the sub-band audio signals obtained by the maximum value obtaining means
60
in the current frame and the maximum value of the amplitudes of the sub-band audio signals obtained by the maximum value obtaining means
60
in the preceding frame exceeds a predetermined threshold value, judging whether or not the number of the sequential frame counted in the third step exceeds a predetermined number.
The conventional microphone-speaker apparatus, however, encounters such a problem that the judgment tends to be mistakenly made by the howling sound judging means
70
that the howling sound is produced while the microphone unit
40
is receiving the audio sound outputted by the speaker unit
80
with being remarkably affected by the amplitude of the audio sound received by the microphone unit under the condition that the microphone unit
40
is continuously receiving the audio sound represented by the raw sound wave having a relatively high amplitude at a relatively long interval.
When the microphone unit
40
is also receiving a background noise having a relatively high level, the judgment tends to be mistakenly made by the howling sound judging means
70
that the howling sound is produced while the microphone unit
40
is receiving the audio sound outputted by the speaker unit
80
under the condition that the microphone unit
40
is continuously receiving the audio sound represented by the raw sound wave having a relatively high amplitude during a relatively long interval.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a microphone-speaker apparatus which can enhance the quality of the audio sound to be outputted by the speaker unit by judging whether or not the howling sound is produced while the microphone unit is receiving the audio sound outputted by the speaker unit without being affected by the amplitude of the audio sound received by the microphone unit.
According to the first aspect of the present invention, there is provided a microphone-speaker apparatus, comprising: a microphone unit for receiving an audio sound represented by a raw sound wave varied in response to a time axis to convert the audio sound to an audio signal, the raw sound wave including a coherent sound wave and an incoherent sound wave, the raw sound wave being constituted by a plurality of raw wave components each having an audio frequency, and the coherent sound wave being constituted by a plurality of coherent wave components each having the audio frequency; a speaker unit for outputting the audio sound to the microphone unit, the audio sound including a howling sound represented by the coherent sound wave, and the howling sound being produced while the microphone unit is receiving the audio sound outputted by the speaker unit; audio signal dividing means for dividing the audio signal converted by the microphone unit into a plurality of raw component signals each indicative of the raw wave components, each of the raw component signals having a plurality of sequential frames divided along the time axis, and the sequential frames each having a current frame and a previous frame prior to the current frame; coherent component signal extracting means for extracting a plurality of coherent component signals respectively indicative of the coherent wave components from the raw component signals divided by the audio signal dividing means, each of the coherent component signals in each of the sequential frames having a raw power value; power value calculating means for calculating the raw power value of each of the coherent component signals extracted by the coherent component signal extracting means; power value adjusting means for adjusting the raw power value of each of the coherent component signals calculated by the power value calculating means to produce an adjusted power value of each of the coherent component signals; power value judging means for judging whether or not the adjusted power value of each of the coherent component signals of the current frame adjusted by the power value adjusting means exceeds the adjusted power value of each of the coherent component signals of the previous frame adjusted by the power value adjusting means; power value ratio calculating means for calculating a power value ratio of the adjusted power value of each of the coherent component signals to an average value of th
Mei Xu
Pearne & Gordon LLP
LandOfFree
Microphone-speaker apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Microphone-speaker apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Microphone-speaker apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3250724