Acoustic Feedback Suppression Using Adaptive Filtering and Peak Smoothing

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Solution Overview

Problem

Conventional howling suppression technologies face challenges in accurately detecting and stably suppressing howling caused by acoustic feedback from a speaker to a microphone, particularly when multiple frequencies are involved, leading to difficulties in distinguishing howling from voice signals.

Innovation Solution

A howling suppression device utilizing an adaptive filter to estimate acoustic feedback characteristics, an estimator to calculate frequency domain amplitude characteristics, and a suppression gain calculator to smooth frequency peaks, thereby stabilizing howling suppression.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional howling suppression methods using notch filters are used, then howling at detected frequencies can be suppressed, but stable suppression is difficult when multiple frequencies are involved and howling may be mistaken for voice signals

Engineering Contradiction:

Improvehowling suppression stabilityVSAvoidfrequency detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent transforms the howling suppression problem from time domain to frequency domain by applying Fourier transform. This parameter change allows precise identification of howling frequencies and application of frequency-specific suppression gains, resolving the instability issue when multiple frequencies are involved while maintaining accurate frequency detection through spectral analysis

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements dynamic suppression gain calculation that adapts to changing acoustic conditions. The suppression gain is continuously updated based on real-time frequency domain analysis, allowing the system to respond to varying howling conditions while distinguishing between howling and voice signals through their different spectral characteristics

Inventive Principle:

Principle #15Dynamics

2Reliability

If frequency domain processing is applied to suppress howling, then frequency peaks can be smoothed, but computational load increases

Engineering Contradiction:

Improvehowling suppression stabilityVSAvoidcomputational load

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies suppression gain locally to specific frequency bins where howling occurs, rather than processing the entire frequency spectrum uniformly. This localized approach targets only the problematic frequency peaks with smoothing operations, achieving stable howling suppression while minimizing unnecessary computational operations in non-howling frequency regions

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS12581234B2Howling suppression device, howling suppression method, and non-transitory computer readable recording medium storing howling suppression program

Publication Date: 2026.03.17 PANASONIC INTELLECTUAL PROPERTY CORP OF AMERICA

AI summary

A howling suppressing device includes: an adaptive filter that estimates an acoustic feedback characteristic representing a characteristic of an acoustic feedback sound reaching a microphone from a speaker by defining an output signal to the speaker as a reference signal, and eliminates the acoustic feedback sound from an input signal obtained via the microphone by using the estimated acoustic feedback characteristic; an estimator that estimates, on the basis of the acoustic feedback characteristic, an acoustic feedback amplitude frequency characteristic in a frequency domain; a suppression gain calculator that calculates, from the acoustic feedback amplitude frequency characteristic, a suppression gain in the frequency domain for smoothing a frequency peak of the acoustic feedback amplitude frequency characteristic; and a suppressor that suppresses an output signal from the adaptive filter in the frequency domain by using the suppression gain.