Audio Signal Frequency Distortion for Feedback Suppression
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Solution Overview
Problem
Existing methods for frequency distortion in audio signals to suppress acoustic feedback often result in unpleasant overlaps between frequency-distorted and non-frequency-distorted signal bands, particularly in systems with high tonal content, leading to artifacts like beat frequencies and rattling noises due to the finite edge gradient of filters.
Innovation Solution
A method where the audio signal is divided at a division frequency located between two neighboring tones of a tonal system, with either the high-frequency or low-frequency band being frequency-distorted, while maintaining a minimum distance from the tones to minimize overlap effects, and using a frequency shift that can be constant or dependent on the audio signal's frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency distortion is applied to suppress acoustic feedback, then feedback suppression is improved, but unpleasant overlaps and artifacts occur in the output signal
Solution Approach 1:
The patent applies different quality treatments to different frequency regions by selecting a division frequency that separates tonal and non-tonal signal bands. The frequency distortion is applied selectively to non-tonal components while tonal components remain undistorted, creating local quality differences that suppress feedback without generating unpleasant artifacts in the tonal regions.
Solution Approach 2:
The patent performs preliminary analysis of the input signal to identify tonal components before applying frequency distortion. By detecting the presence and characteristics of tonal signals in advance, the system can prepare appropriate processing paths that prevent artifact generation while maintaining effective feedback suppression.
2Reliability
If frequency distortion is applied to decorrelate output signal from input signal, then feedback suppression effectiveness is improved, but signal cancellation and artifacts occur in tonal regions
Solution Approach 1:
The patent implements local quality by applying frequency distortion only to non-tonal signal components while preserving tonal components unchanged. This selective approach ensures that feedback suppression effectiveness is maintained in non-tonal regions through decorrelation, while tonal regions avoid signal cancellation and artifact generation by remaining undistorted.
Solution Approach 2:
The patent introduces an intermediary mechanism that detects tonal components and mediates between the need for frequency distortion (for feedback suppression) and the need to preserve tonal signals (to avoid artifacts). The tonal detection system acts as an intermediary that routes signals through appropriate processing paths.
3Reliability
If adaptive filter is used for feedback compensation, then feedback suppression is improved, but tonal signals are completely cancelled out
Solution Approach 1:
The patent applies local quality by implementing different compensation strategies for different signal types. Tonal signals receive preservation treatment while non-tonal signals receive aggressive feedback compensation through the adaptive filter. This local differentiation allows effective feedback compensation without complete cancellation of tonal signals.
Solution Approach 2:
The patent applies partial action by using the adaptive filter selectively rather than uniformly across all frequency regions. The filter is applied excessively to non-tonal components where feedback suppression is critical, while tonal components receive partial or no filtering to preserve signal integrity and avoid complete cancellation.
Data Source
AI summary
A method performs frequency distortion of an audio signal. The audio signal is divided at at least one division frequency into a low-frequency band and a high-frequency band. A frequency-distorted signal is generated through respectively different distortions of frequencies for the high-frequency band and for the low-frequency band. The division frequency is selected such that it is located between two neighboring tones of a given tonal system.