Directional Microphone Signal Incidence Localization
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Solution Overview
Problem
Existing methods for determining the direction of incidence of acoustic signals using directional microphone systems are inaccurate for small microphone separations and are ambiguous in open-air environments due to symmetrical sensitivity distributions, especially when used in hearing aids where head-related transfer functions (HRTFs) interfere with signal localization.
Innovation Solution
The method involves producing directional microphone signals through a weighted combination of signals from at least two microphones, with weightings that create direction-dependent sensitivity distributions, allowing for unambiguous determination of the signal incidence by identifying the direction of the sensitivity minimum, and accounting for the influence of the acoustic environment, including HRTFs, to achieve precise localization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If correlation analysis methods are used for direction determination, then direction estimation can be performed, but accuracy deteriorates for small microphone separations (less than one sampling period)
Solution Approach 1:
The patent changes the parameter of delay time from discrete sampling periods to continuous sub-sampling period delays. By allowing delay times to be fractions of a sampling period (e.g., 0.5ms, 0.75ms), the system achieves accurate direction estimation even with microphone separations smaller than one sampling period, resolving the accuracy limitation of conventional correlation methods.
2Device complexity
If two or more microphones are arranged on one axis for direction estimation, then the system structure is simplified, but measurement precision deteriorates due to symmetrical sensitivity distributions causing ambiguous direction determination
Solution Approach 1:
The patent introduces asymmetry into the sensitivity distribution by optimizing the weighting factors in the directional microphone signal. This creates an asymmetric sensitivity pattern where the minimum sensitivity direction is uniquely defined, eliminating the 180-degree ambiguity that plagues symmetric arrangements. The asymmetric weighting allows unambiguous direction determination while maintaining the simple linear microphone arrangement.
3Adaptability or versatility
If head-related transfer functions (HRTFs) are present in hearing aid applications, then the system can be worn on the head, but measurement precision deteriorates due to corruption of direction estimation results
Solution Approach 1:
The patent performs preliminary optimization of the directional microphone signal weighting factors to account for the expected HRTF influence. By pre-configuring the weighting to compensate for head-related acoustic effects, the system maintains accurate direction estimation even when worn on the head, effectively counteracting the corrupting influence of HRTFs before they degrade measurement precision.
Data Source
AI summary
To determine the direction of incidence for a signal from an acoustic signal source using a directional microphone system, which has at least two microphones, two or more directional microphone signals are produced, each having a direction-dependent sensitivity distribution with a minimum in one direction. The directional microphone signals are assessed with regard to a quantity to determine the directional microphone signal which is most influenced by the associated direction dependent sensitivity distribution. The direction of incidence is determined as being the direction in which the minimum of the sensitivity distribution of this directional microphone signal is located.