SoundCompass: a distributed MEMS microphone array-based sensor for sound source localization

Sound source localization is a well-researched subject with applications ranging from localizing sniper fire in urban battlefields to cataloging wildlife in rural areas. One critical application is the localization of noise pollution sources in urban environments, due to an increasing body of evidence linking noise pollution to adverse effects on human health. Current noise mapping techniques often fail to accurately identify noise pollution sources, because they rely on the interpolation of a limited number of scattered sound sensors. Aiming to produce accurate noise pollution maps, we developed the SoundCompass, a low-cost sound sensor capable of measuring local noise levels and sound field directionality. Our first prototype is composed of a sensor array of 52 Microelectromechanical systems (MEMS) microphones, an inertial measuring unit and a low-power field-programmable gate array (FPGA). This article presents the SoundCompass's hardware and firmware design together with a data fusion technique that exploits the sensing capabilities of the SoundCompass in a wireless sensor network to localize noise pollution sources. Live tests produced a sound source localization accuracy of a few centimeters in a 25-m2 anechoic chamber, while simulation results accurately located up to five broadband sound sources in a 10,000-m2 open field

A Geometric Approach to Sound Source Localization from Time-Delay Estimates

This paper addresses the problem of sound-source localization from time-delay estimates using arbitrarily-shaped non-coplanar microphone arrays. A novel geometric formulation is proposed, together with a thorough algebraic analysis and a global optimization solver. The proposed model is thoroughly described and evaluated. The geometric analysis, stemming from the direct acoustic propagation model, leads to necessary and sufficient conditions for a set of time delays to correspond to a unique position in the source space. Such sets of time delays are referred to as feasible sets. We formally prove that every feasible set corresponds to exactly one position in the source space, whose value can be recovered using a closed-form localization mapping. Therefore we seek for the optimal feasible set of time delays given, as input, the received microphone signals. This time delay estimation problem is naturally cast into a programming task, constrained by the feasibility conditions derived from the geometric analysis. A global branch-and-bound optimization technique is proposed to solve the problem at hand, hence estimating the best set of feasible time delays and, subsequently, localizing the sound source. Extensive experiments with both simulated and real data are reported; we compare our methodology to four state-of-the-art techniques. This comparison clearly shows that the proposed method combined with the branch-and-bound algorithm outperforms existing methods. These in-depth geometric understanding, practical algorithms, and encouraging results, open several opportunities for future work.Comment: 13 pages, 2 figures, 3 table, journa

On directivity of a circular arraywith directional microphones

© 2016 IEEE. Circular microphone arrays have a broad range of applications in teleconferencing and hands-free telecommunication systems. Directional microphones are extensively used to construct the circular arrays to obtain superior sound quality. However, the 360-degree coverage ability of this type of circular arrays is seldom investigated. In this paper, we develop a circular array with the use of four firstorder supercardioid microphones to obtain 360-degree coverage of sound recording in teleconferencing environments. Through analyzing the directional response of this array, we derive an optimal range of the array radius for uniform 360-degree coverage of sound capturing. Experiments are carried out in an anechoic chamber to test the performance of the developed microphone array

MINIATURE LOW-COHERENCE FIBER OPTIC ACOUSTIC SENSOR WITH THIN-FILM UV POLYMER DIAPHRAGM

A miniature low-coherence fiber optic acoustic sensor with a thin-film UV polymer diaphragm is developed and studied in this thesis to address the fundamental challenge of miniaturizing acoustic sensors. When miniaturizing an acoustic sensor, there is a critical size limitation at which the transduction mechanism deformation becomes too small for detection. However, a solution to this problem is to utilize a high resolution, low coherence fiber optic interferometric detection system coupled with a soft, thin-film transduction mechanism. A novel fabrication technique was developed to enable the use of elastomers, which inherently exhibit desirably low Young's modulus properties. In addition, the fabrication process enables fabrication of diaphragms at thicknesses on the order of nanometers. The fabrication process also renders highly tunable sensor performance and superior sensing quality at a low cost. The sensor developed exhibits a flat frequency response between 50 Hz and 4 kHz with a useable bandwidth up to 20 kHz, a dynamic range of 117.55 dB SPL, a signal to noise ratio (SNR) of 58 dB, and a sensitivity up to 1200 mV/Pa. In this thesis, it is further demonstrated that by using an array these sensors fabricated from the same batch facilitates accurate directional sound localization by utilizing the interaural phase difference (IPD) exhibited by sensor pairs. Future work is suggested to optimize the sensor performance for a specific application, to carry out studies of more complex array configurations, and to develop algorithms that can help increase the sound localization accuracy

Ambisonics

This open access book provides a concise explanation of the fundamentals and background of the surround sound recording and playback technology Ambisonics. It equips readers with the psychoacoustical, signal processing, acoustical, and mathematical knowledge needed to understand the inner workings of modern processing utilities, special equipment for recording, manipulation, and reproduction in the higher-order Ambisonic format. The book comes with various practical examples based on free software tools and open scientific data for reproducible research. The book’s introductory section offers a perspective on Ambisonics spanning from the origins of coincident recordings in the 1930s to the Ambisonic concepts of the 1970s, as well as classical ways of applying Ambisonics in first-order coincident sound scene recording and reproduction that have been practiced since the 1980s. As, from time to time, the underlying mathematics become quite involved, but should be comprehensive without sacrificing readability, the book includes an extensive mathematical appendix. The book offers readers a deeper understanding of Ambisonic technologies, and will especially benefit scientists, audio-system and audio-recording engineers. In the advanced sections of the book, fundamentals and modern techniques as higher-order Ambisonic decoding, 3D audio effects, and higher-order recording are explained. Those techniques are shown to be suitable to supply audience areas ranging from studio-sized to hundreds of listeners, or headphone-based playback, regardless whether it is live, interactive, or studio-produced 3D audio material

Surround by Sound: A Review of Spatial Audio Recording and Reproduction

In this article, a systematic overview of various recording and reproduction techniques for spatial audio is presented. While binaural recording and rendering is designed to resemble the human two-ear auditory system and reproduce sounds specifically for a listener’s two ears, soundfield recording and reproduction using a large number of microphones and loudspeakers replicate an acoustic scene within a region. These two fundamentally different types of techniques are discussed in the paper. A recent popular area, multi-zone reproduction, is also briefly reviewed in the paper. The paper is concluded with a discussion of the current state of the field and open problemsThe authors acknowledge National Natural Science Foundation of China (NSFC) No. 61671380 and Australian Research Council Discovery Scheme DE 150100363