Multi-Microphone Feedforward ANC for Multi-Directional Noise Cancellation
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Solution Overview
Problem
Existing active noise cancellation (ANC) systems face challenges in accurately modeling the dynamic acoustic environment, leading to suboptimal noise cancellation due to changing noise sources and directions, especially when multiple noise sources are present.
Innovation Solution
A multi-microphone feedforward ANC system with at least two reference signals captured by feedforward microphones, which are filtered using individual transfer functions to generate a feedforward signal that effectively cancels noise from various directions, improving noise cancellation performance by modeling the acoustic paths and combining signals to achieve better interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single microphone feedforward ANC system is used, then the system complexity is low, but the noise cancellation performance is limited to one source direction only
Solution Approach 1:
The patent divides the noise cancellation task into multiple segments by using multiple microphones (at least two feedforward microphones) positioned at different locations. Each microphone captures noise from different directions, and the system processes each microphone's signal separately through individual filters before combining them. This segmentation allows the system to handle noise from multiple source directions simultaneously while maintaining manageable processing complexity for each individual channel.
Solution Approach 2:
The patent combines the outputs of multiple individual filters (each processing signals from different microphones) to generate a composite feedforward signal. By merging the filtered signals from multiple microphones through a combination process (such as summation or weighted combination), the system achieves comprehensive noise cancellation coverage for noise arriving from multiple directions, effectively combining the capabilities of individual microphone channels.
2Measurement precision
If individual filters are determined based on linear combinations of transfer functions, then the noise cancellation accuracy improves, but the processing complexity increases
Solution Approach 1:
The patent performs preliminary determination of individual filters based on linear combinations of transfer functions before actual noise cancellation operation. By pre-calculating and storing the filter coefficients that represent the acoustic paths from multiple microphone positions to the eardrum, the system prepares the necessary processing parameters in advance. This preliminary action enables accurate real-time noise cancellation without requiring complex real-time calculations during operation.
Solution Approach 2:
The patent changes the parameters of individual filters by determining them as linear combinations of multiple transfer functions. Instead of using a single transfer function, the system adjusts and optimizes filter parameters by combining multiple transfer function representations, thereby improving the accuracy of noise prediction and cancellation while systematically managing the increased processing requirements through structured parameter optimization.
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 multi-microphone system achieves robust noise cancellation across a wider frequency range and multiple noise directions, providing better performance than single-microphone systems by accurately accounting for the dynamic acoustic environment and noise source locations.
Implementation Method 1
Each of the at least two reference signals includes at least one captured acoustic sound representing an unwanted noise
Implementation Method 2
The anti-noise acoustic wave is intended to attenuate or eliminate the background noise at the listening position via destructive interference
Implementation Method 3
The compensation signal is provided to an audio transducer (e.g., a loudspeaker) which generates an 'anti-noise' acoustic wave
Data Source
AI summary
Systems and methods for active noise cancellation are provided. An example method includes receiving at least two reference signals associated with at least two reference positions. Each of the at least two reference signals includes at least one captured acoustic sound representing an unwanted noise. The reference signals are filtered by individual filters to obtain filtered signals. The filtered signals are combined to obtain a feedforward signal. The feedforward signal is played back to reduce the unwanted noise at a pre-determined space location. The individual filters are determined based on linear combinations of at least two transfer functions. Each of the at least two transfer functions is associated with one of the reference positions. In certain embodiments, the at least two reference signals are captured by at least two feedforward microphones.