Anti-Noise Signal Generator With Dual-Path Low-Latency Filtering
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Solution Overview
Problem
Conventional digital active noise cancellation (ANC) systems suffer from high latency due to discrete-time sampling, which introduces phase shifts and affects noise cancellation performance, while analogue systems are difficult to tune.
Innovation Solution
A tuneable anti-noise signal generator using a combination of sigma-delta modulated signals and dual digital filtering paths, where one path operates at a high sampling frequency for low latency and the other at a lower frequency for flexibility, allowing for reduced system latency and ease of tuning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If digital filters are used for active noise cancellation, then the system is more easily tuneable, but the system latency increases
Solution Approach 1:
The digital filter is divided into two separate filtering paths: a first filtering path that processes sigma-delta modulated signals with minimal processing for low latency, and a second filtering path that operates at a lower sampling rate for easier tuning. This segmentation allows each path to be optimized for its specific function, resolving the contradiction between tuneability and latency.
Solution Approach 2:
The system dynamically switches between or combines results from the two filtering paths depending on the operational requirements. The first path provides rapid response for time-critical noise cancellation, while the second path provides adjusted filtering for tonal noise, enabling the system to adapt its processing characteristics to different noise conditions and priorities.
2Loss of time
If high sampling frequency is used to minimize latency, then the system latency is reduced, but the processing complexity increases
Solution Approach 1:
The processing load is segmented between two paths: the first path handles high-frequency sigma-delta modulated signals with simplified processing to maintain low latency, while the second path operates at lower sampling rates with more complex filtering algorithms for tonal noise, distributing the processing complexity across different operational domains.
Solution Approach 2:
Different processing qualities are applied to different noise components: the first filtering path applies minimal processing suitable for broadband noise requiring low latency, while the second filtering path applies more sophisticated processing suitable for tonal noise where latency is less critical but filtering precision is important.
Data Source
AI summary
An anti-noise signal generator and a method of generating an anti-noise signal are presented. The anti-noise generator includes a first microphone input to receive a first sigma-delta modulated signal at a microphone sampling frequency. The first microphone input is coupled to a combiner via a first path and a second path. The combiner is adapted to combine a first filtered signal from the first path and a second filtered signal from the second path to generate the anti-noise signal. The first path includes a first digital filter adapted to operate at a filter frequency equal or greater than the microphone sampling frequency. The second path includes a second digital filter. The first digital filter may be a sigma-delta based filter that includes a sigma-delta modulator.