Audio Equalization with Error Microphone for ANC Stability
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Solution Overview
Problem
Active noise cancellation (ANC) technologies face challenges in effectively reducing ambient noise, particularly at higher frequencies, and maintaining stability, which can affect the intelligibility of reproduced audio signals in devices like headphones and headsets, especially when ambient noise from one ear affects the user.
Innovation Solution
A method and apparatus that incorporate an error microphone to generate an acoustic error signal, an ANC module to produce an anti-noise signal, and an equalizer to modify the audio signal spectrum based on noise estimates, enhancing noise cancellation and intelligibility by combining anti-noise and equalized audio signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If active noise cancellation is applied to reduce ambient noise, then noise reduction level is improved, but stability and intelligibility of reproduced audio signals deteriorate
Solution Approach 1:
The audio signal processing is segmented into multiple independent modules: ANC module for noise cancellation, equalizer for frequency adjustment, and intelligibility enhancement module for clarity improvement. Each module processes specific aspects of the audio signal independently, allowing optimization of noise reduction without compromising overall system stability and intelligibility.
Solution Approach 2:
The system employs feedback mechanisms where the output of the ANC module and equalizer is continuously monitored and adjusted by the intelligibility enhancement module. This feedback loop ensures that noise cancellation efforts do not degrade the intelligibility of reproduced audio signals, maintaining stability while achieving noise reduction.
2Object-affected harmful factors
If active noise cancellation is applied to reduce ambient noise, then noise reduction level is improved, but intelligibility of reproduced audio signals deteriorates
Solution Approach 1:
The equalizer performs preliminary frequency adjustment on the audio signal before it enters the ANC module. By pre-emphasizing important frequency ranges and shaping the spectral content, the system ensures that critical audio information is preserved and enhanced before noise cancellation processing, preventing intelligibility loss.
Solution Approach 2:
The system dynamically adjusts multiple parameters including equalizer frequency response, gain levels, and ANC filter coefficients to optimize both noise reduction and intelligibility. By changing these parameters adaptively based on ambient conditions, the system maintains high audio intelligibility while achieving effective noise cancellation.
3Object-affected harmful factors
If noise cancellation is enhanced across broader frequency range, then noise reduction effectiveness is improved, but device complexity increases
Solution Approach 1:
The audio processing system is designed with multi-functional modules that serve multiple purposes: the equalizer not only adjusts frequency response but also shapes noise spectra; the ANC module handles both noise cancellation and signal stabilization; the intelligibility enhancement module provides both clarity improvement and artifact suppression. This multi-functionality reduces overall system complexity while achieving broad frequency range noise reduction.
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
The solution effectively reduces ambient noise across a broader frequency range, improving the intelligibility of audio signals and maintaining stability in ANC systems, even when ambient noise from one ear is present.
Implementation Method 1
an error microphone arranged to be directed during use of the device at the ear canal of an ear of the user and to produce an acoustic error signal in response to a sensed acoustic error
Implementation Method 2
an ANC module arranged to produce an anti-noise signal based on information from the acoustic error signal
Implementation Method 3
an equalizer arranged to modify a spectrum of the audio signal based on information from the acoustic error signal and the noise estimate
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3A~3C
AI summary
Methods and apparatus for generating an anti-noise signal and equalizing a reproduced audio signal (e.g., a far-end telephone signal) are described, wherein the generating and the equalizing are both based on information from an acoustic error signal.