Frequency-Domain Echo Suppression Filter for Residual Echo Removal
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Solution Overview
Problem
Existing echo suppressors in hands-free cellular telephones are unable to completely eliminate far-end echo, leading to residual echo issues during voice communication.
Innovation Solution
The method involves using a frequency domain approach by dividing the magnitude of the frequency domain representation of a reference signal by the magnitude of an LMS-filtered error signal, then multiplying the result by the frequency domain representation of the reference signal to obtain a signal with reduced residual frequency components, which is converted back to the time domain to suppress echo effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If LMS filtering is used to suppress echo, then echo suppression is improved, but residual echo components remain
Solution Approach 1:
The patent introduces a frequency domain processing intermediary between the LMS filter and the final output. The LMS-filtered signal is transformed to frequency domain, where a frequency response is computed and used to further suppress residual echo components before converting back to time domain. This intermediary frequency domain processing step acts as a mediator that enhances the echo suppression capability beyond what LMS filtering alone can achieve.
Solution Approach 2:
The patent changes the domain parameter from time domain (LMS filtering) to frequency domain for additional processing. By transforming the signal to frequency domain, computing a frequency response, and applying frequency domain filtering, the system exploits frequency domain characteristics to suppress residual echo that remained after time domain LMS filtering. This parameter change enables access to different signal characteristics that are not apparent in the time domain.
2Illumination intensity
If speaker output amplitude is increased for driver hearing, then audio quality is improved, but echo pickup by microphone increases
Solution Approach 1:
The patent extracts and removes the harmful echo components from the microphone signal. The frequency response computation identifies the speaker output spectrum, and this information is used to extract and suppress the corresponding echo components from the microphone signal in the frequency domain. This extraction process separates the desired speech from the unwanted echo, allowing the speaker to output at sufficient levels without compromising audio quality.
Data Source
AI summary
Residual frequency components of a reference signal are suppressed from an error signal. A magnitude of the frequency domain representation of the reference signal is divided by a magnitude of the frequency domain representation of LMS-filtered representation of the error signal to obtain a frequency domain ratio of the frequency domain representation of the reference signal to the frequency domain representation of the LMS-filtered signal. The frequency domain ratio of the frequency domain representation of the reference signal to the frequency domain representation of the LMS-filtered signal is multiplied by the frequency domain ratio of the frequency domain representation of the reference signal to the frequency domain representation of the LMS-filtered signal, to obtain a frequency domain signal having reduced residual frequency components of the reference signal.