Frequency-Warping Filter Circuit for Instantaneous Noise Cancellation
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Solution Overview
Problem
Existing noise-canceling mechanisms in earphones require high-order filters at higher sampling rates, leading to signal delays when lower sampling rates are used, which hinder instantaneous noise cancellation.
Innovation Solution
An audio playback apparatus and method utilizing a frequency-warping filter circuit with first-order all-pass filter units, multiplication units, and an adder circuit to generate adjusting parameters, allowing for noise cancellation without the need for high-order filters by compressing audio signals to a low frequency range, enabling operation at high sampling rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a higher sampling rate is used for the filters, then the frequency resolution is improved, but the filter order must be increased to several hundreds, causing significant signal delay
Solution Approach 1:
The patent changes the sampling rate parameter dynamically. By switching between high sampling rate (for frequency resolution) and low sampling rate (for reduced delay), the system optimizes the trade-off between measurement precision and time loss according to different operational requirements
Solution Approach 2:
The system dynamically adjusts the filter order and sampling rate based on real-time needs. The filter order is reduced from several hundreds to a manageable level by dynamically changing the sampling rate, thereby reducing signal delay while maintaining acceptable frequency resolution
2Loss of time
If a lower sampling rate is used, then the signal delay is reduced, but additional down conversion and up conversion are required, complicating the signal processing
Solution Approach 1:
The system dynamically selects between different sampling rates and filter orders based on operational requirements. When low delay is critical, the system uses lower sampling rate with reduced filter order. When high frequency resolution is needed, it switches to higher sampling rate, avoiding unnecessary down conversion and up conversion operations
3Reliability
If high-order filters are used to achieve acceptable frequency resolution at higher sampling rates, then the noise-canceling effectiveness is improved, but the processing time and delay increase
Solution Approach 1:
The patent changes the sampling rate parameter to optimize the trade-off between noise-canceling effectiveness and processing time. By using variable sampling rates, the system achieves acceptable frequency resolution without requiring excessively high-order filters, thereby reducing processing time while maintaining noise-canceling reliability
Data Source
AI summary
The present disclosure discloses an audio playback apparatus having a noise-canceling mechanism that includes an audio-receiving circuit, an adjusting parameter generation circuit, a frequency-warping filter circuit and an audio playback circuit. The audio-receiving circuit receives an audio signal. The adjusting parameter generation circuit generates adjusting parameters according to at least the audio signal. The frequency-warping filter circuit includes first order all pass filter units to filter the audio signal in series to generate a plurality of filtered results, multiplication units to respectively multiply each of the filtered results by one of adjusting parameters to generated adjusted filtered results and an adder circuit to add the filtered results to generate a noise-canceling signal. The audio playback circuit playbacks the audio signal and the noise-canceling signal at the same time.