Howling Canceller Selective Notch Filter Suppression
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Solution Overview
Problem
Existing howling cancellers are ineffective in distinguishing which acoustic feedback loop is experiencing howling when multiple microphones are used, leading to suppression of unnecessary frequency components in non-affected loops.
Innovation Solution
A howling canceller that compares frequency components of sound signals from multiple microphones to identify the frequency with maximum power and selectively inserts a notch filter to suppress only the frequency causing howling, preventing unnecessary suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all howling cancellers connected to multiple microphones allot notch filters to the same frequency when howling is detected in any loop, then howling suppression is achieved across all loops, but frequency components that should not be suppressed are unnecessarily suppressed in loops where howling does not occur
Solution Approach 1:
The patent divides the howling suppression control into independent segments for each acoustic feedback loop. Each howling canceller independently determines whether to allot a notch filter based on its own loop's howling detection result, rather than all cancellers uniformly responding to any detected howling. This segmentation allows selective suppression only in the specific loop experiencing howling, preventing unnecessary suppression in other loops.
Solution Approach 2:
The patent applies local quality by making each howling canceller's notch filter allotment decision specific to its local acoustic feedback loop conditions. Instead of a global uniform suppression approach, each canceller independently evaluates its own loop's howling state and applies suppression only where needed, creating locally optimized suppression behavior that avoids affecting other loops.
2Adaptability or versatility
If a plurality of microphones is used to form multiple acoustic feedback loops, then sound signal coverage is improved, but it becomes difficult to identify which specific loop is experiencing howling
Solution Approach 1:
The patent segments the howling detection and suppression functions into independent units, with each howling canceller responsible for its own acoustic feedback loop. This segmentation allows each canceller to independently detect and respond to howling in its specific loop without interference from other loops, effectively solving the identification problem even with multiple microphones.
Solution Approach 2:
The patent introduces an intermediary control mechanism where each howling canceller acts as an independent intermediary between its specific acoustic feedback loop and the notch filter suppression function. This intermediary structure allows precise control and identification of which loop requires suppression, eliminating the confusion that would arise from centralized control of multiple loops.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses howling in the correct acoustic feedback loop while avoiding unnecessary frequency suppression, thereby minimizing sound signal deterioration.
Implementation Method 1
a howling suppressing unit performing suppression processing of detecting frequency components at which howling is possibly occurring in sound signals picked up by a plurality of microphones, comparing the detected frequency components with each other on a per-frequency basis, detecting a frequency component having maximum power, and suppressing the frequency component having the maximum power in the sound signal including the frequency component having the maximum power
Data Source
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Figure 2(A)~2(B)
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AI summary
A howling canceller is adapted to an acoustic system having a speaker and first and second microphones. The speaker and the first microphone form a first acoustic feedback loop; the speaker and the second microphone form a second acoustic feedback loop. The howling canceller includes a howling suppressing unit for performing suppression processing in such a way that: frequency components at which howling is possibly occurring are detected in each of the sound signals picked up by the first and second microphones; the detected frequency components of the sound signals picked up by the first and second microphones are compared with each other on a per-frequency basis and a frequency component having larger power is detected; and based on the comparison results, the larger power frequency component of at least one of the sound signals picked up by the first and second microphones is suppressed.