Hearing Device Clock Adjustment via Buffer Feedback
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Solution Overview
Problem
The mismatch in system clock frequencies between wirelessly connected hearing devices leads to inaccurate timing relationships and sample overflow/underflow events, degrading the perceptual quality of binaural beamformed audio signals, particularly in head-wearable devices with limited precision, temperature drift, and power consumption constraints.
Innovation Solution
A method to adjust the system clock frequency of a slave hearing device by detecting overflow and underflow events in the receipt and transmit buffers, using a digital processor to increase or decrease the frequency in predefined steps, synchronized with the master device's clock frequency, and employing near-field magnetic coupling for wireless communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate crystal-based clock generators are used in each hearing device, then device independence and wireless communication are enabled, but clock frequency mismatch and timing inaccuracies occur due to production tolerances and temperature drift
Solution Approach 1:
The patent implements a feedback mechanism where the slave device continuously monitors buffer overflow and underflow events caused by clock frequency mismatch. Based on this feedback, the slave device automatically adjusts its clock frequency in predefined steps to minimize timing errors and maintain accurate synchronization with the master device, thereby resolving the contradiction between device independence and clock accuracy
Solution Approach 2:
The slave device dynamically changes its clock frequency parameter in response to detected timing errors. By adjusting the clock frequency in predefined steps based on buffer status, the system adapts to temperature drift and production tolerances while maintaining synchronization, thus resolving the contradiction between using separate independent clocks and achieving accurate timing
2Measurement precision
If higher precision clock generators are used, then timing accuracy between devices is improved, but device size, cost, and power consumption increase
Solution Approach 1:
The system uses the existing low-power crystal-based clock generators in each device and adds a self-service synchronization mechanism. The slave device autonomously monitors its own buffer status and adjusts its clock frequency without requiring external intervention or higher-power reference clocks, thus achieving accurate timing while maintaining low power consumption and small device size
Solution Approach 2:
The patent introduces buffer overflow/underflow detection as an intermediary mechanism that translates timing errors into actionable feedback. This intermediary allows the system to achieve high timing accuracy through software-based clock adjustment rather than requiring expensive, high-precision hardware clock generators, thereby reducing power consumption and device size
3Reliability
If buffer realignment procedures are used to handle overflow events, then data loss is prevented, but audio signal latency increases and perceptual quality degrades
Solution Approach 1:
The system performs preliminary clock frequency adjustment by the slave device based on predicted timing errors from buffer status monitoring. By proactively adjusting the clock frequency before significant overflow or underflow events occur, the system prevents data loss without needing frequent buffer realignment operations, thus maintaining low latency and high audio quality
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach minimizes clock skew, reduces latency, and enhances the perceptual quality of binaural audio processing by maintaining accurate timing alignment between the devices, even with limited precision clock generators, while being compact, inexpensive, and low-power.
Implementation Method 1
employing near-field magnetic coupling for wireless communication
Data Source
AI summary
The present disclosure relates in one aspect to methods of adjusting a second system clock frequency of a slave or second device to a first system clock frequency of a first device connectable thereto via a unidirectional or bidirectional wireless data communication link so to reduce clock skew between the first and second system clock frequencies.