Wireless Audio Clock Synchronization for Echo Cancellation
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Solution Overview
Problem
In wireless digital audio conferencing systems, unsynchronized clocks at the base station and wireless microphones make it difficult to align audio signal samples for effective acoustic echo cancellation, leading to incomplete removal of echo components in microphone signals.
Innovation Solution
Synchronizing the clocks used for sampling at the base station and wireless microphones with a common master reference clock ensures that audio information can be aligned in time, allowing for accurate echo cancellation by using the synchronized sampling clocks to control the sampling rate and align audio information captured at both locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If wireless microphones use independent local oscillators for sampling, then device complexity is reduced, but timing alignment between base station and microphone samples deteriorates
Solution Approach 1:
The patent merges the clock synchronization function by having the base station distribute timing information to wireless microphones. The base station's master clock synchronizes all sampling operations across the system, combining multiple independent timing sources into a unified timing reference that ensures precise alignment between base station and microphone samples.
2Device complexity
If acoustic echo cancellation is performed with unsynchronized sampling, then device complexity is reduced, but echo cancellation effectiveness deteriorates
Solution Approach 1:
The patent implements feedback mechanisms where the base station continuously monitors and adjusts timing information distributed to wireless microphones. This feedback loop ensures that sampling clocks remain synchronized despite variations in wireless transmission conditions, maintaining reliable echo cancellation effectiveness.
3Ease of manufacture
If sampling occurs at different times due to clock drift, then implementation is simpler, but audio signal alignment deteriorates
Solution Approach 1:
The patent applies preliminary action by having the base station pre-synchronize its master clock with the wireless microphones before audio sampling begins. Timing information is distributed in advance to establish a common time reference, ensuring that all sampling operations occur at aligned times without requiring complex real-time adjustments during audio processing.
Data Source
AI summary
A digital audio conferencing system has a fixed base station that is in communication with a far end (R.E.) system over a communication network. The base station is associated with a wireless loudspeaker and one or more wireless microphones. The base station operates to receive F.E. audio signals to be played by the wireless loudspeaker, and it operates to remove acoustic echo picked up by the wireless microphones. A first clock controlling F.E. audio signal sampling at the base station, and a second clock controlling audio signal sampling and at a wireless microphone are synchronized to one master, reference clock that controls the operation of the base station. Acoustic echo included in an audio signal picked up by a wireless microphone is removed by AEC functionality running in the base station.