Patent ID: 7133529
Filing Date: 2006-11-07
Classification: H04R

Abstract:
1. A howling detecting and suppressing apparatus for detecting and suppressing howling sound components comprising: a frequency dividing processing section for converting a plurality of sound time signal segments each corresponding to a time segment into a plurality of sound frequency signal segments each corresponding to a frequency segment; a howling suppressing section for respectively adjusting gains for said sound frequency signal segments converted by said frequency dividing processing section to generate howling-suppressed sound frequency signal segments; a howling detecting section for judging whether a howling sound component is present or not for each of said howling-suppressed sound frequency signal segments generated by said howling suppressing section to detect howling sound frequency signal segments each in which it is judged that said howling sound component is present and non-howling sound frequency signal segments each in which it is judged that said howling sound component is not present; and a frequency synthesizing processing section for synthesizing said howling-suppressed sound frequency signal segments suppressed by said howling suppressing section to generate howling-suppressed sound time signal segments, and in which said howling suppressing section is operative to respectively adjust gains for said sound frequency signal segments converted by said frequency dividing processing section by changing the gains of said howling sound frequency signal segments detected by said howling detecting section and passing through said non-howling sound frequency signal segments detected by said howling detecting section said frequency dividing processing section is operative to convert a plurality of sound time signal segments collected for a predetermined number of sample periods into a plurality of sound frequency signal segments collectively forming one frame; said howling detecting section includes: a delay generator for respectively delaying said howling-suppressed sound frequency signal segments collectively forming a frame generated by said howling suppressing section for a predetermined number of frames to be outputted as reference frequency signal segments collectively forming a frame; an adaptive filter for respectively convolving said reference frequency signal segments outputted by said delay generator with coefficients to generate adapted reference frequency signal segments collectively forming a frame; a coefficient updating calculating section for respectively updating said coefficients on the basis of said sound howling-suppressed sound frequency signal segments generated by said howling suppressing section, said reference frequency signal segments outputted by said delay generator, and said adapted reference frequency signal segments generated by said adaptive filter; a frequency power calculating section for respectively calculating frequency signal powers of said adapted reference frequency signal segments collectively forming a frame generated by said adaptive filter; a smoothing processing section for respectively smoothing said frequency signal powers of said adapted reference frequency signal segments collectively forming a frame calculated by said frequency power calculating section to generate smoothed frequency signal powers of said adapted reference frequency signal segments collectively forming a frame; a total average frequency power calculating section for inputting said smoothed frequency signal powers of said adapted reference frequency signal segments collectively forming a frame generated by said smoothing processing section to calculate a total average value of said smoothed frequency signal powers of said frame; a power ratio calculating section for inputting frequency signal power ratios of said smoothed frequency signal powers of said adapted reference frequency signal segments collectively forming said frame generated by said smoothing processing section to respectively calculate frequency signal power ratios of said smoothed frequency signal powers of said adapted reference frequency signal segments thus inputted to said total average value of said frequency signal powers of said frame calculated by said total average frequency power calculating section to respectively generate frequency signal power ratios each corresponding to frequency segments in said frame; a power ratio comparing section for respectively comparing said frequency signal power ratios in said frame calculated by said power ratio calculating section with a predetermined first howling detecting threshold value to detect howling frequency signal power ratios and howling frequency segments respectively corresponding to said howling frequency signal power ratios in said frame each of which exceeds said first howling detecting threshold value from among said frequency signal power ratios; a target frame counting section for respectively counting the number of target frames in which said howling frequency signal power ratios are detected by said power ratio comparing section with respect to said howling frequency segments; and a howling judging section for judging whether a howling sound component is present or not for each of said howling frequency segments by comparing the number of target frames counted by said target frame counting section with respect to each of said howling frequency segments detected by said power ratio comparing section and a predetermined second howling detecting threshold value to detect howling sound frequency signal segments each in which it is judged that said howling sound component is present because of the fact that the number of target frames counted by said target frame counting section with respect to said howling frequency segment exceeds said second howling detecting threshold value and non-howling sound frequency signal segments each in which it is judged that said howling sound component is not present because of the fact that the number of target frames counted by said target frame counting section with respect to said howling frequency segment does not exceed said second howling detecting threshold value.