Earphone ANC Filter Generation Using Adaptive Acoustic Path Estimation
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Solution Overview
Problem
Existing active noise reduction earphones face challenges in accurately determining the transfer functions of acoustic paths, leading to increased errors in noise reduction due to variations in directivity, sound source location, and individual ear anatomy, making it difficult to obtain precise noise reduction.
Innovation Solution
A method involving an earphone with a feedback microphone and adaptive filtering algorithm to calculate the transfer function of the active noise reduction filter by obtaining a physically noise-reduced signal and a mixed signal, allowing for the generation of an active noise reduction filter without needing to calculate the transfer functions of the physical and playing acoustic paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transfer functions H1 and H3 are obtained separately to calculate H2, then the noise reduction function can be implemented, but the measurement errors of P(z) and G(z) will superpose and greatly increase the error of estimating H2
Solution Approach 1:
The patent merges the measurement of P(z) and G(z) into a single combined measurement process. Instead of separately measuring the physical acoustic path P(z) and playing acoustic path G(z), the method measures their product P(z)G(z) directly through the feedback microphone, thereby avoiding the superposition of measurement errors that would occur with separate measurements.
Solution Approach 2:
The feedback microphone serves as an intermediary that directly captures the combined effect of both acoustic paths. By using the feedback microphone signal as the measurement intermediary, the system obtains P(z)G(z) directly without needing to separately characterize each path, thus eliminating error accumulation.
2Reliability
If separate measurements of P(z) and G(z) are performed, then the transfer function H2 can be calculated, but the complexity of measurement and calibration increases
Solution Approach 1:
The patent combines the measurement of two separate acoustic paths into a single unified measurement. By measuring the combined transfer function P(z)G(z) directly through the feedback microphone rather than separately measuring P(z) and G(z), the calibration process is simplified from requiring two separate measurements to requiring only one combined measurement.
Solution Approach 2:
The patent extracts the combined transfer function information directly from the feedback microphone signal without needing to extract and process separate P(z) and G(z) components. This extraction approach simplifies the measurement process by obtaining the necessary information in a single step rather than through multiple separate measurements and calculations.
Data Source
AI summary
A method for generating an active noise reduction filter includes: obtaining a physically noise-reduced signal, the physically noise-reduced signal being a signal received by a feedback microphone after a noise signal passes through an earphone, obtaining a mixed signal, the mixed signal being a signal received by the feedback microphone when the same noise signal is played and the earphone plays a through signal in a through state, calculating an input signal according to the mixed signal and the physically noise-reduced signal, performing adaptive filtering on the input signal and the physically noise-reduced signal according to an adaptive filtering algorithm to obtain a transfer function, and generating an active noise reduction filter according to the transfer function.