Adaptive Beam Forming for Microphone Array Noise Compensation
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Solution Overview
Problem
Conventional Beam Forming methods with small microphone spacing suffer from poor signal-to-noise ratio, especially at lower frequencies, due to amplification of intrinsic noise and spatial aliasing issues, and fail to effectively compensate for microphone tolerances and wind buffeting.
Innovation Solution
An adaptive Beam Forming method that transforms sound signals into complex-valued frequency-domain signals, calculates a Beam Focus Spectrum with time-dependent attenuation factors, and uses a Characteristic Function to limit signal components, compensating for microphone tolerances and wind buffeting, thereby improving signal-to-noise ratio and reducing unwanted amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional Beam Forming methods are used with small microphone spacing, then the device size is reduced, but the signal-to-noise ratio deteriorates due to amplification of intrinsic noise
Solution Approach 1:
The patent applies preliminary action by calculating and storing attenuation factors for each frequency component before actual beam forming operation. The system pre-processes the microphone signals to determine the appropriate attenuation levels that will be applied during directional signal extraction, thereby preventing noise amplification before it occurs
Solution Approach 2:
The patent changes parameters by introducing frequency-dependent attenuation factors that dynamically adjust the gain applied to each frequency component. Instead of uniform amplification, the system modifies the attenuation parameters based on the spectral characteristics of the incoming signals, reducing attenuation for frequencies prone to noise amplification while maintaining it for directional signals
2Device complexity
If conventional Beam Forming methods are used with small microphone spacing, then the device complexity is reduced, but spatial aliasing issues occur at lower frequencies
Solution Approach 1:
The system performs preliminary analysis of the spectral content from multiple microphones before applying beam forming weights. By pre-calculating attenuation factors based on the observed signal characteristics, the system proactively prevents spatial aliasing artifacts from appearing in the output, rather than attempting to correct them afterward
Solution Approach 2:
The patent introduces an intermediary processing stage that acts as a mediator between the raw microphone signals and the final beam formed output. This intermediate stage calculates attenuation factors that reconcile the conflicting requirements of maintaining directional sensitivity while suppressing spatial aliasing, effectively decoupling these two functions
3Object-affected harmful factors
If simple noise reduction methods are applied, then the noise level is reduced, but the voice quality degrades under high noise conditions
Solution Approach 1:
The patent applies local quality by treating different frequency components differently through frequency-dependent attenuation factors. Instead of applying uniform noise reduction across all frequencies, the system selectively attenuates specific frequency bands where noise is present while preserving the spectral characteristics of voice signals, thereby maintaining voice quality even under high noise conditions
Solution Approach 2:
The system applies partial action by selectively applying attenuation only to frequency components that exhibit noise characteristics. Rather than uniformly reducing all signals or aggressively suppressing all noise, the patent applies moderate, frequency-specific attenuation that removes noise while preserving voice quality, avoiding the excessive action that would degrade speech
4Device complexity
If microphone tolerances are not compensated, then the system simplicity is maintained, but the beam forming accuracy deteriorates
Solution Approach 1:
The patent compensates for microphone tolerances by dynamically adjusting the attenuation factors applied to signals from individual microphones. The system modifies the processing parameters for each microphone based on its specific characteristics, thereby equalizing their contributions to the beam formed output without requiring complex hardware calibration or replacement
Data Source
AI summary
A method and apparatus are provided for adaptively generating a directional output signal from sound received by at least two microphones arranged as microphone array. The method includes transforming the sound received by each of the microphones and represented by analog-to-digital converted time-domain signals into corresponding complex-valued frequency-domain microphone signals each having a frequency component value for each of a plurality of frequency components, calculating from the complex-valued frequency-domain microphone signals a Beam Focus Spectrum by means of an Adaptive Spectrum that is calculated as quotient of conditionally updated moving temporal averages of complex-valued products of frequency-domain microphone signals, multiplying, for each of the plurality of frequency components, the attenuation factor with the frequency component value of the complex-valued frequency-domain microphone signal to obtain a directional frequency component value, and forming a frequency-domain directional output signal.