Echo Suppression Device Non-Linear Gain Control
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Solution Overview
Problem
Existing echo suppression techniques fail to adequately suppress echoes in environments where the microphone and speaker are closely positioned, such as in-vehicle hands-free phones, leading to distortion and non-linear echo signals that do not meet standards like those set by the eCall system in Europe or Russia.
Innovation Solution
An echo suppression device that utilizes a combination of linear and non-linear filters, along with a distortion suppression gain deciding unit and distortion correcting unit, to calculate and apply a gain based on the power of the reference signal and cross-correlation values, effectively suppressing non-linear distortions in echo signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the microphone and speaker are disposed close to each other to achieve compact device structure, then the device size is reduced, but the echo signal becomes very high and causes distortion in the input sound signal
Solution Approach 1:
The echo suppression process is divided into multiple stages: first a linear filter suppresses general echo, then a non-linear filter specifically targets distorted echo components. This segmentation allows each filter to specialize in different types of echo suppression, effectively handling the distortion problem caused by close microphone-speaker positioning.
Solution Approach 2:
The patent dynamically adjusts the gain parameter of the non-linear filter based on the power level of the reference signal. When the reference signal power exceeds a threshold (indicating high echo conditions), the gain is reduced to suppress distorted echo. This parameter adaptation allows the system to respond to varying echo conditions in real-time.
2Device complexity
If conventional linear filters are used for echo suppression, then the implementation is simple, but the echo is not sufficiently suppressed when the echo signal is very large and causes distortion
Solution Approach 1:
The patent combines a linear filter and a non-linear filter into a composite echo suppression system. The linear filter handles standard echo conditions while the non-linear filter specifically addresses distorted echo components. This composite approach leverages the strengths of both filter types to achieve superior echo suppression effectiveness.
Solution Approach 2:
The non-linear filter acts as an intermediary component between the linear filter and the final output. It receives the signal from the linear filter, applies non-linear processing to suppress distorted echo components, and produces the final suppressed signal. This intermediary structure allows the system to handle both linear and non-linear echo characteristics.
3Measurement precision
If the gain is increased to amplify weak echo signals, then the echo suppression sensitivity is improved, but the distortion in the signal is exacerbated
Solution Approach 1:
The gain of the non-linear filter is dynamically adjusted based on the power level of the reference signal. When the reference signal power is high (indicating strong echo), the gain is reduced to prevent distortion. When the power is lower, the gain can be increased for better sensitivity. This dynamic adaptation allows the system to maintain optimal performance across different signal conditions.
Solution Approach 2:
The system uses the power of the reference signal as feedback to control the gain parameter of the non-linear filter. This feedback mechanism allows the system to automatically adjust its suppression characteristics based on the current echo conditions, maintaining both sensitivity and distortion control.
Data Source
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AI summary
An echo suppression device includes a processor, the device includes a suppressing unit configured to generate a corrected sound signal by suppressing an echo signal representing an echo generated by collecting, by a sound input unit, a sound arising from a reproduction sound signal reproduced by a sound output unit; a distortion suppression gain deciding unit configured to obtain a gain to attenuate the corrected sound signal according to a degree of distortion of the echo signal with which intensity of the echo signal non-linearly changes with respect to an intensity change of the reproduction sound signal; and a distortion correcting unit configured to suppress the corrected sound signal according to the gain.