Echo Reduction Circuitry Using Spectral Mask Training Sequences
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Solution Overview
Problem
Modern digital voice communication systems face challenges in echo cancellation due to high computational complexity and disturbances from ambient noise and changing acoustic environments, leading to difficulties in suppressing echoes, especially when multiple users speak simultaneously or when the echo environment changes.
Innovation Solution
The implementation of an echo-reduction circuitry that generates training signals inserted into digital audio signals below the noise floor, using a training sequence and spectral mask to estimate filter coefficients and generate echo-cancellation signals, allowing for effective echo removal even in complex acoustic environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional echo cancellation algorithms are used in modern digital voice communication systems, then echo suppression may be achieved, but the algorithms fail to converge fast enough when both persons are talking simultaneously, and may fail to converge when the echo environment changes
Solution Approach 1:
The patent inserts a training sequence into the audio signal before echo cancellation processing. This preliminary action provides the echo canceller with known reference data that accelerates convergence and ensures reliable operation even when both parties are speaking simultaneously or when acoustic environments change. The training sequence is generated by filtering a pseudo-random sequence through a spectral mask derived from the audio signal's power spectrum.
2Object-generated harmful factors
If echo cancellers simulate the acoustic echo path to eliminate feedback, then echo suppression is achieved, but the computational complexity becomes excessively high
Solution Approach 1:
The patent extracts only the essential information needed for echo cancellation by inserting a compact training sequence rather than processing the entire audio signal through complex adaptive filtering. The training sequence contains sufficient information for the echo canceller to adapt quickly without requiring extensive computational resources for full acoustic path simulation.
3Productivity
If packetization and compression techniques are used in digital voice communication, then transmission efficiency is improved, but latency increases making echo cancellation more difficult
Solution Approach 1:
The patent employs a feedback mechanism where the training sequence is inserted into the transmitted audio signal, received back through the communication channel, and used to train the echo canceller. This closed-loop approach allows the system to adapt to the actual transmitted and received signal characteristics, compensating for delays introduced by packetization and compression while maintaining echo cancellation effectiveness.
Data Source
AI summary
Embodiments of an audio communication device and methods for reducing echoes are generally described herein. Other embodiments may be described and claimed. In some embodiments, echo-reduction circuitry may insert a training signal into digital audio signals at or below a noise floor and in a non-audible portion of the frequency spectrum based on a spectral mask. The training signal may be generated from a spectrum estimate and a training sequence. An adaptive filter may generate an echo-cancellation signal using filter coefficients generated from the training sequence and return-path signals. The echo-cancellation signal may remove echo signals from the return-path signals.