High-Accuracy Sound Source Localization Using MEMS Microphone Arrays

Introduction

Sound source localization and Direction of Arrival (DOA) estimation have become crucial technologies across various applications including robotics, security systems, structural health monitoring, and smart devices. At SISTC, we specialize in developing advanced MEMS microphone solutions that power these innovative applications.

Drawing from research conducted at Illinois Institute of Technology, this article explores how MEMS-based acoustic sensor arrays can achieve high-precision sound source localization and DOA estimation in controlled environments.

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Understanding Sound Source Localization and DOA Estimation

Sound source localization involves determining the spatial position of an acoustic source using multiple receivers, while DOA estimation focuses solely on identifying the direction of the sound source. Both methods rely on time difference of arrival (TDOA) or phase difference information, combined with strategic sensor array geometry.

Typical implementation involves three key steps:

Multi-channel data acquisition
Phase or time-delay calculation
Position or direction computation

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Advanced MEMS Microphone Array Data Acquisition

The research utilized an FPGA-based system known as MEMS Array Acoustic Imaging (MASI) platform, which offers:

Simultaneous sampling from 52 omnidirectional MEMS microphones
Sampling rates up to 300 kSPS
High-speed data transfer via Gigabit Ethernet
Real-time signal processing capabilities

Built on the CAPTAN architecture, this system provides exceptional modularity and scalability for various acoustic testing scenarios.

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Experimental Setup: Controlled Acoustic Environment

To ensure accurate measurements, researchers developed a specialized 52″×52″×27″ anechoic chamber lined with high-density polyester foam to absorb sound reflections. This controlled environment, combined with a modular sensor test stand, allowed for precise testing of various sensor configurations and geometries.

Key Experimental Findings

DOA Estimation in Reflective Environments

Initial tests in standard laboratory environments showed significant accuracy degradation due to background noise and reflections, highlighting the importance of controlled testing conditions.

Improved Accuracy in Anechoic Chamber

Moving experiments to the anechoic chamber substantially reduced reflections and improved measurement accuracy, though some systemic errors remained.

Optimized Receiver Configuration

By increasing microphone spacing, using foam isolation, and adjusting source frequencies (700Hz and 900Hz), researchers achieved significantly better alignment with theoretical values.

Pulse Signal Advantage

Using 20-cycle sine pulses and analyzing only the first arriving wavefront eliminated multipath interference, enabling highly accurate DOA estimation even at longer distances.

Ultrasonic Localization Applications

Further experiments using 40kHz ultrasonic transducers demonstrated sub-inch accuracy in both 2D and 3D localization, opening possibilities for high-precision applications in robotics and industrial automation.

See ultrasonic localization in robotics applications

Conclusion and Applications

This research demonstrates that combining MEMS microphone arrays with FPGA-based data acquisition and controlled acoustic environments enables highly accurate sound source localization and DOA estimation. Key success factors include:

Minimizing reflections and environmental noise
Optimizing sensor geometry and signal types
Implementing short pulses to avoid multipath distortion

These advancements support applications in:

Robotic auditory systems
Voice-controlled interfaces
Security and surveillance systems
Industrial monitoring and automation

References:
Kunin, V., Turqueti, M., Sanite, J., & Oruklu, E. (2011). Direction of Arrival Estimation and Localization Using Acoustic Sensor Arrays. Journal of Sensor Technology.

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