Multi-Focus Beam-Forming Signal Processing for Vehicle Noise Reduction
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Solution Overview
Problem
Existing noise reduction methods for hands-free communication systems, especially in vehicles, face challenges with high noise levels, microphone array tolerances, and wind buffeting, leading to degraded signal quality and signal-to-noise ratios when using multiple microphones.
Innovation Solution
The method generates a directional output signal with multiple Beam Focus Directions by transforming microphone signals into frequency-domain signals, calculating Beam Focus Spectra with real-valued attenuation factors, and multiplying these factors with frequency components to create a multi-focus directional output signal, while compensating for microphone tolerances and reducing wind noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multiple microphones are used to reduce noise, then noise reduction capability is improved, but microphone tolerances and wind buffeting degrade signal quality
Solution Approach 1:
The patent applies preliminary calibration to determine transfer functions for each microphone before actual noise reduction operation. This preliminary action characterizes each microphone's individual tolerances and wind buffeting effects, enabling the system to compensate for these factors during signal processing and maintain high signal quality while using multiple microphones for noise reduction
Solution Approach 2:
The system uses feedback through calculated transfer functions that model each microphone's response characteristics. By continuously applying these transfer functions to adjust the combined signal, the system compensates for microphone tolerances and wind effects, maintaining signal quality while achieving noise reduction through multiple microphone input
2Measurement precision
If microphones are positioned far apart to distinguish voice levels, then voice signal differentiation is improved, but noise cancellation effectiveness deteriorates
Solution Approach 1:
The patent changes the parameter of microphone spacing from large distances to small distances, and compensates for the resulting reduced voice signal differentiation through digital signal processing using transfer functions. This allows maintaining close microphone positioning for effective noise cancellation while using calibration-based parameter adjustment to preserve voice signal distinction capability
3Device complexity
If simple subtraction method is used for noise reduction, then device complexity is reduced, but noise reduction effectiveness deteriorates
Solution Approach 1:
The patent applies preliminary calibration to determine transfer functions that characterize each microphone's response. This preliminary action enables the system to use enhanced processing methods with multiple transfer function applications rather than simple subtraction, improving noise reduction effectiveness while keeping the overall device complexity manageable through systematic preprocessing
Solution Approach 2:
The patent introduces transfer functions as intermediary elements between the raw microphone signals and the final processed output. These transfer functions act as mediators that systematically adjust each microphone signal based on calibrated characteristics, providing effective noise reduction through a structured intermediate processing step rather than direct simple subtraction
4Measurement precision
If feature detection is used to estimate time differences, then noise reduction accuracy is improved, but processing complexity and difficulty increase
Solution Approach 1:
The patent applies preliminary calibration to determine transfer functions that encode time difference information. This preliminary action transforms the difficult real-time feature detection problem into a simpler application of pre-computed transfer functions, maintaining high time difference estimation accuracy while dramatically reducing processing difficulty and complexity during operation
Data Source
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AI summary
A method and apparatus are provided for generating a directional output signal from sound received by at least two microphones arranged as microphone array. The directional output signal has one or more Beam Focus Directions. The method includes transforming sound received by each microphone into a corresponding complex valued frequency-domain microphone. For any Beam Focus Direction a Beam Focus Spectrum is calculated, consisting, for each of the plurality of frequency components, of time-dependent, real-valued attenuation factors being calculated based on the plurality of microphone signals. For each of the plurality of frequency components, the maximum amongst those attenuation factors of different Beam Focus Spectra is selected and multiplied with the frequency component of the complex-valued frequency-domain signal of one microphone, forming a frequency-domain multi-focus directional output signal, from which by means of inverse transformation a time-domain signal can be synthesized.