Patent ID: 6674863
Filing Date: 2004-01-06
Classification: H04R

Abstract:
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, said raw sound wave including a coherent sound wave, said raw sound wave being constituted by a plurality of raw wave components each having an audio frequency, and said coherent sound wave being constituted by a plurality of coherent wave components; a speaker unit for outputting said audio sound to said microphone unit, said audio sound including a howling sound represented by at least one coherent sound wave, and said howling sound being produced while said microphone unit is receiving said audio sound outputted by said speaker unit; audio signal dividing means for dividing an audio signal indicative of said audio sound received by said microphone unit into a plurality of raw component signals each indicative of said raw wave components, each of said raw component signals having a plurality of sequential frames divided along said time axis, and said sequential frames each having a current frame and a previous frame prior to said current frame; coherent component signal extracting means for extracting a plurality of coherent component signals respectively indicative of said coherent wave components from said raw component signals divided by said audio signal dividing means, each of said coherent component signals in each of said sequential frames having a raw power value; power value calculating means for calculating said raw power value of each of said coherent component signals extracted by said coherent component signal extracting means; power value adjusting means for adjusting said raw power value of each of said coherent component signals calculated by said power value calculating means to produce an adjusted power value of each of said coherent component signals; power value judging means for judging whether or not said adjusted power value of each of said coherent component signals is increased along said time axis; power value ratio calculating means for calculating a power value ratio of said adjusted power value of each of said coherent component signals to an average value of said adjusted power values of said coherent component signals; power value ratio judging means for judging whether or not said power value ratio of said adjusted power value of each of said coherent component signals to said average value of said adjusted power values of said coherent component signals exceeds a predetermined threshold value; howling sound judging means for judging whether or not said howling sound is produced while said microphone unit is receiving said audio sound outputted by said speaker unit during periodic intervals based on each of results judged by said power value judging means and results judged by said power value ratio judging means; and howling sound suppressing means for suppressing said howling sound based on results judged by said howling sound judging means.