Microphone Array Asymmetry for Acoustic Source Separation
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Solution Overview
Problem
Existing microphone arrays face challenges in accurately localizing sound sources in reverberant environments due to interference from acoustic barriers and directional asymmetry, which affect the measurement of sound pressure gradients and directional sensitivity.
Innovation Solution
A microphone array design with strategically placed barriers and varying sensor spacings to equalize sound pressure differences across different directions, ensuring that the error in measured sound direction is minimized, typically within 45°, and compensating for directional asymmetry produced by the support structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sensors are placed close together on the support means to simplify manufacturing, then ease of manufacture is improved, but measurement precision deteriorates due to directional asymmetry and acoustic interference
Solution Approach 1:
The patent applies asymmetry by intentionally creating asymmetric acoustic environments for different sensor pairs. Barriers are selectively placed between specific sensor pairs (e.g., first and second sensors) but not between others (e.g., first and third sensors), creating controlled asymmetric conditions that compensate for the directional asymmetry introduced by the planar support structure. This allows the system to maintain manufacturing simplicity while achieving accurate sound direction measurement.
Solution Approach 2:
The patent uses acoustic barriers as intermediary elements placed between specific sensor pairs. These barriers mediate the acoustic interaction by controlling sound wave propagation paths, preventing direct acoustic interference between certain sensors while allowing other sensors to receive sound waves more directly. This intermediary approach resolves the contradiction by managing acoustic interference without requiring complex sensor arrangements.
2Measurement precision
If barriers are added between sensors to control acoustic interference, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by placing barriers only in specific locations between certain sensor pairs rather than uniformly across all sensors. The barriers are locally positioned to address specific acoustic interference problems between particular sensor combinations, leaving other areas unaffected. This selective local intervention achieves measurement precision improvement without requiring comprehensive system-wide modifications.
3Measurement precision
If sensor spacing is increased to reduce acoustic interference, then measurement precision is improved, but the directional sensitivity and ability to detect sound direction deteriorates
Solution Approach 1:
The patent applies parameter changes by carefully controlling and optimizing the spacing parameters between sensors and barriers. Specific spacing relationships are established between sensors and between barriers and sensors to achieve optimal acoustic conditions. By adjusting these spatial parameters, the system maintains sufficient sound pressure gradient detection capability while reducing acoustic interference, thereby improving measurement precision without compromising sound direction detection ability.
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 system achieves directional selective sound reception with improved accuracy in localizing sound sources across a 360° range, reducing errors in sound component direction measurement and enhancing the separation of acoustic signals from multiple sources.
Implementation Method 1
the systems described in WO 2009/050487 and PCT/GB2013/050784 work by measuring pressure gradient within the sound wave between different microphones in the array
Implementation Method 2
the formation of acoustic pressure gradients, and thereby ability of the algorithm of PCT/GB2013/050784 to localise sounds, can be manipulated by inserting acoustic barriers or other objects between microphone capsules
Data Source
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AI summary
A system for directionally selective sound reception comprises an array of pressure sensors (120a, 120c) each arranged to output a pressure signal indicative of pressure, and a processor arranged to receive the pressure signals. The sensor array comprises a support (130)supporting the four sensors. Two of the sensors are mounted on one side of the support and at least a third sensor is supported on an opposite side of the support. The sound pressure difference measured between the first sensor and the second sensor caused by sound arriving at the array from a direction parallel to the support (130) is dependent on the distance between the first and second sensors and the nature of material in the space between the first and second sensors. The sound pressure difference measured between the first and third sensors caused by sound travelling perpendicular to the support is dependent on the distance between the first and third sensors. The nature of material in the space between the first and third sensors, and the spacings and the materials are selected such that the sound pressure differences are substantially equal.