Wireless Hearing Aid Clock Synchronization via Packet Timing Feedback
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Solution Overview
Problem
Existing audio systems, such as hearing assistance systems, face challenges in maintaining synchronized sample clocks between audio source and sink devices over wireless communication links, leading to audio sample over-runs or under-runs and undesirable artifacts, especially when packets are lost due to interference.
Innovation Solution
The synchronization of sample clocks is achieved through a packet-based method using an adjustable oscillator, with link layer information aiding in packet loss concealment and phase lock loop jitter reduction, allowing for accurate synchronization and artifact-free audio playback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sample clocks are synchronized using traditional methods, then audio playback can proceed, but audio sample over-runs or under-runs occur causing artifacts
Solution Approach 1:
The patent implements a feedback mechanism where the receiving device measures the arrival time of audio packets and compares it with expected timing. This timing information is fed back to adjust the local sample clock, creating a closed-loop synchronization system that prevents over-runs and under-runs, thereby resolving the contradiction between maintaining playback and ensuring synchronization accuracy.
Solution Approach 2:
The patent uses preliminary action by pre-synchronizing sample clocks before audio transmission begins. The system establishes timing relationships and adjusts clock frequencies in advance, so that when audio packets are transmitted, the receiving device is already prepared to process them without over-runs or under-runs, improving both reliability and synchronization precision.
2Manufacturing precision
If factory calibration is performed to ensure clock synchronization, then audio fidelity improves, but production costs increase
Solution Approach 1:
The patent enables self-service by allowing the hearing instrument to automatically synchronize its sample clock with the audio source device during operation. The device uses built-in timing measurement and adjustment capabilities to maintain synchronization without requiring external factory calibration, thereby achieving high audio fidelity while reducing production costs.
Solution Approach 2:
The patent dynamically changes the sample clock parameters (frequency, phase) based on real-time packet arrival timing. This adaptive parameter adjustment allows the system to maintain precise synchronization and high audio fidelity without fixed factory calibration, reducing manufacturing complexity and cost.
3Reliability
If packet loss concealment is not used, then system complexity is reduced, but audio quality deteriorates when packets are lost
Solution Approach 1:
The patent applies partial action by implementing packet loss concealment only when packet loss is detected, rather than continuously processing all audio data with concealment algorithms. This selective application maintains audio quality during packet loss events while minimizing the added processing complexity during normal operation.
Data Source
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AI summary
An audio system such as a hearing assistance system includes an audio source device wirelessly communicating with one or more audio sink (destination) devices. The audio source and sink devices each include a sample clock for processing audio signal that is digitized and wirelessly transmitted. The sample clock of each of the one or more audio sink devices is synchronized to the sample clock of the audio source device to prevent audio sample over-runs or under-runs causing undesirable audio artifacts. In one embodiment, because audio packets may be lost in transmission, packet loss concealment techniques are used to improve audio reproduction. In one embodiment, link layer information is used for audio phase lock loop jitter reduction in the audio system.