Headphone ANC and Noise Compensation Across Frequency Bands
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Solution Overview
Problem
Existing headphone technologies face limitations in effectively combining active noise cancellation and noise compensation, particularly in enhancing audio quality by addressing high-frequency noise and varying noise sources and listener positions, which affect the accuracy of noise estimation and sound reproduction.
Innovation Solution
An audio processing device with a selector and noise compensation unit that selects transfer functions based on features of external noise and content audio signals to compute gains for noise compensation, considering dependencies on signal levels and directivity, thereby transforming noise and audio signals to improve perceived quality and audibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If active noise cancellation is used to reduce external noise, then noise level at eardrum is reduced, but high-frequency noise cancellation effectiveness is limited due to hardware constraints
Solution Approach 1:
The patent divides noise control into two separate frequency bands: active noise cancellation for low-frequency noise (below 1500 Hz) and noise compensation for high-frequency noise (above 1500 Hz). This segmentation allows each technique to operate in its optimal frequency range, overcoming the hardware limitations of active noise cancellation at high frequencies while maintaining effective noise control across the entire audible spectrum.
2Measurement precision
If noise compensation boosts audio signal in high noise spectral regions, then perceived audio quality is improved, but audio signal distortion may occur in low noise regions
Solution Approach 1:
The noise compensation technique applies frequency-dependent gain adjustment to the audio signal, boosting only those frequency regions where background noise significantly degrades audio quality. The compensation filter derives different gains for different frequency bands based on measured noise characteristics, thereby improving perceived audio quality in noisy spectral regions while avoiding unnecessary distortion in clean spectral regions.
3Object-affected harmful factors
If combined active noise cancellation and noise compensation are implemented, then overall noise control and audio quality are improved, but device complexity increases
Solution Approach 1:
The patent integrates active noise cancellation and noise compensation into a unified audio processing system where both techniques operate simultaneously on the audio signal. The combined system processes low-frequency noise through active cancellation and high-frequency noise through compensation, achieving superior overall noise control and audio quality enhancement while managing system complexity through coordinated operation of both techniques.
Data Source
AI summary
The disclosure relates to combined active noise cancellation and noise compensation in a headphone. An audio processing device includes a selector and a noise compensation unit. The selector can select one of a plurality of first transfer functions based on at least one feature of at least one of an external noise and a content audio signal representing a sound to be reproduced through the headphone. The noise compensation unit can compute a second audio signal by applying the selected first transfer function to a first audio signal, and derive gains for the noise compensation at least based on the second audio signal. The at least one feature can be used to distinguish at least two of the first transfer functions. Each of the first transfer functions can transform the first audio signal to the second audio signal which is assumed as representing a version of the sound represented by the first audio signal, which arrives at an eardrum of a listener wearing the headphone. The first audio signal is one of a noise signal representing the external noise and the content audio signal.