Variable Group Delay Audio Filter for Low-Latency Noise Suppression
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Solution Overview
Problem
Existing audio output systems in personal devices face challenges in achieving low latency while minimizing out-of-band noise, as conventional filtering methods introduce undesirable delay and power dissipation.
Innovation Solution
A system with a filter configured to receive digital audio signals quantized at specific levels and sampled at high frequencies, featuring a selectable variable group delay, a digital-to-analog converter, and a driver to generate filtered analog audio signals with minimal latency and effective noise reduction, utilizing a low-pass filter with adjustable characteristics to optimize noise cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If out-of-band filtering is applied to reduce noise, then noise reduction is improved, but latency increases
Solution Approach 1:
The filter implements variable group delay that dynamically adapts to different audio signal conditions. The filter can switch between different delay states (e.g., normal delay and reduced delay) depending on whether out-of-band noise is present, allowing optimal balance between noise reduction and latency for different operating conditions
Solution Approach 2:
The filter changes its group delay parameter based on signal analysis. When out-of-band noise is detected, the filter applies appropriate delay for effective noise cancellation. When no out-of-band noise is present, the filter reduces delay to minimize latency, thus adapting the delay parameter to current signal conditions
2Object-affected harmful factors
If conventional filtering is used to minimize out-of-band noise, then noise reduction is improved, but power dissipation increases
Solution Approach 1:
The filter applies out-of-band filtering selectively rather than continuously. It processes only the portions of the signal that contain out-of-band noise components, avoiding unnecessary processing of clean signal portions. This partial action reduces overall power consumption while maintaining effective noise reduction when needed
Solution Approach 2:
The filter dynamically adjusts its operation based on the presence and level of out-of-band noise. When noise levels are high, the filter engages full processing. When noise levels are low or absent, the filter reduces or disables processing, thereby minimizing power dissipation while maintaining noise reduction capability when required
3Object-affected harmful factors
If high sampling frequency is used to reduce noise folding, then noise reduction is improved, but processing complexity increases
Solution Approach 1:
The filtering process is segmented into multiple stages: first, out-of-band noise is identified through signal analysis; second, filtering is applied selectively to remove identified noise components; third, the filtered signal is output. This segmentation allows efficient processing by focusing computational resources only where needed, reducing overall complexity while maintaining high sampling frequency benefits
Data Source
AI summary
A system may include a filter configured to receive a digital audio input signal quantized at between two and 257 quantization levels and sampled at at least 500 kilohertz, the filter further configured to perform filtering on the digital audio input signal to generate a filtered digital audio input signal, the filter having a selectable variable group delay, a digital-to-analog converter configured to receive the filtered digital audio input signal and convert the filtered digital audio input signal into an equivalent analog audio input signal, and a driver configured to receive the equivalent analog audio input signal and drive an analog audio output signal to a transducer.