THURSDAY MORNING, 8 NOVEMBER 2018 THEATER (VCC), 7:45 A.M. TO 12:15 P.M. Session 4aAA Architectural Acoustics, Engineering Acoustics, Signal Processing in Acoustics, and Noise: Microphone Array Applications in Room Acoustics Gary W. Elko, Cochair mh Acoustics, 25A Summit Ave., Summit, NJ 07901 Michael Vorl€ander, Cochair ITA, RWTH Aachen University, Kopernikusstr. 5, Aachen 52056, Germany Chair’s Introduction—7:45 Invited Papers 7:50 4aAA1. Practical open-concentric spherical microphone array design. Mark R. Thomas (Sound Technol. Res., Dolby Labs., 1275 Market St., San Francisco, CA 94103, [email protected]) The problem of higher order sound field capture is considered. First-order microphone arrays, such as tetrahedral A-format designs, are commonplace, while interest remains in the increased spatial resolution delivered by higher order arrays. Such arrays typically consist of pressure microphones mounted on a solid spherical baffle, with which higher-order spatial components are estimated algorith- mically. This produces a design trade-off, with small arrays being preferred for spatial aliasing performance and large arrays being pre- ferred for reduced amplification of microphone capsule noise at low frequencies. A practical open sphere design is proposed that contains microphones mounted at multiple radii to fulfill both criteria. Coupled with the use of cardioid microphones, such an array cap- tures higher order soundfields over a wider audio bandwidth than baffled spherical designs of fixed radius. 8:10 4aAA2. Self-calibration of dual, closed surface microphone arrays. Earl G. Williams (Acoust. Div., Code 7106, Naval Res. Lab., 4555 Overlook Ave., Washington, DC 20375, [email protected]) and William A. Kuperman (Scripps Inst. of Oceanogr., Univ. of California San Diego, La Jolla, CA) With the recent availability of very inexpensive, miniature digital MEMS microphones, the construction of large count microphone arrays is financially within the reach of the basic researcher. Using various mathematical techniques such as the Helmholtz-Kirchhoff in- tegral and the equivalent source method (ESM), dual surface microphone arrays provide the ability to separate incident and scattered fields instantaneously in time. When these arrays form a closed surface, this separation is extremely accurate. However, one of the con- cerns with any microphone array is the calibration of the individual elements, especially near the resonance frequency of the diaphragm. In this paper, a self-calibration technique is proposed, based on ESM, that uses external loudspeakers in a simple laboratory facility not required to be anechoic. The approach is tested numerically on a dual surface, 256 element pair spherical microphone array, and uses an algorithm for the minimization of a cost function based on the extinction of the scattered field when the unknown individual calibration 4a THU. AM coefficients of the array elements are varied. Use of a Burton-Miller approach to model the ESM sources of the scattered field improves dramatically the accuracy at specific frequencies. The problematic interior Dirichlet eigenfrequencies are addressed. [Work supported by the Office of Naval Research.] 8:30 4aAA3. Characterizing acoustic environments using spherical loudspeaker and microphone arrays. Hannes Gamper, Keith Godin, Nikunj Raghuvanshi, and Ivan J. Tashev (Res., Microsoft, One Microsoft Way, Redmond, WA 98052, [email protected]) Room acoustic parameters, including the reverberation time (T60) and the direct-to-reverberant ratio (DRR), quantitatively describe the behaviour of an acoustic environment. These parameters are typically derived from an acoustic impulse response (AIR) obtained using an omnidirectional sound source and an omnidirectional receiver. However, the acoustic interaction between a source with a com- plex radiation pattern, for example, a human talker, and a receiver with a complex directivity pattern, for example, a human listener, can- not be accurately described by an omnidirectional AIR or the acoustic parameters derived from it. Here, we propose characterizing acoustic environments while taking the source and receiver directionality into account. A spherical loudspeaker array allows modelling a source with an arbitrary radiation pattern. Analogously, a spherical microphone can be used to describe a receiver with an arbitrary di- rectivity pattern. By combining spherical loudspeaker and microphone arrays, a multiple-input multiple-output (MIMO) AIR of an acoustic environment can be measured to simulate sources and receivers with arbitrary directivities and estimate acoustic parameters accordingly. 1881 J. Acoust. Soc. Am., Vol. 144, No. 3, Pt. 2, September 2018 ASA Fall 2018 Meeting/2018 Acoustics Week in Canada 1881 8:50 4aAA4. The room impulse response in time, frequency, and space: Mapping spatial energy using spherical array beamforming techniques. Matthew T. Neal and Michelle C. Vigeant (Graduate Program in Acoust., Penn State Univ., 201 Appl. Sci. Bldg., University Park, PA 16802, [email protected]) The auditory perception of rooms is a multi-dimensional problem. Our hearing system interprets time, frequency, and spatial infor- mation from arriving room reflections, but traditionally, only the time and frequency domains are considered in room acoustic metric and objective sound field analyses. This work aims to develop spatial visualizations of the energy in a room impulse response (RIR). With a spherical microphone array, a room’s energy can be mapped in full three-dimensions. First, beamforming techniques are used to generate a set of directional RIRs from the spherical microphone array measurement. This set of directional RIRs is analogous to using a microphone with a directional beam pattern response, oriented individually at all points around a sphere. Then, these directional or beam RIRs are time windowed and band-pass filtered to create spatial energy maps of the room. Comparisons between a plane-wave beam pat- tern and a Dolph-Chebyshev beam pattern will be demonstrated in the context of RIR beamforming. As well, different strategies for nor- malizing peak energy amplitudes to either the direct sound or a spherical spreading condition will be compared. With these considerations, final results of these spatial energy visualizations and directional RIR animations will be demonstrated. [Work supported by NSF Award 1302741.] 9:10 4aAA5. Model-based direction of arrival estimations for sound sources using a spherical microphone array. Christopher R. Landschoot (Architectural Acoustics, Rensselaer Polytechnic Inst., 54 West Main St., Clifton Springs, NY 14432, crlandschoot@gmail. com), Jonathan Mathews, Jonas Braasch, and Ning Xiang (Architectural Acoustics, Rensselaer Polytechnic Inst., Troy, NY) In many room acoustics and noise control applications, it is often challenging to identify the directions of arrivals (DoAs) of incom- ing sound sources. This work seeks to solve this problem reliably by beamforming, or spatially filtering, incoming sound data with a spherical microphone array via a probabilistic method. When estimating the DoA, the signal under consideration may contain one or multiple concurrent sound sources originating from different directions. This leads to a two-tiered challenge of first identifying the cor- rect number of sources, followed by determining the directional information of each source. To this end, a probabilistic method of model-based Bayesian analysis is leveraged. This entails generating analytic models of the experimental data, individually defined by a specific number of sound sources and their locations in physical space, and evaluating each model to fit the measured data. Through this process, the number of sources is first estimated, and then the DoA information of those sources is extracted from the model being the most concise to fit the experimental data. This paper will present the analytic models, the Bayesian formulation, and preliminary results to demonstrate the potential usefulness of this model-based Bayesian analysis for complex noise environments with potentially multiple concurrent sources. 9:30 4aAA6. Iterative echo labeling technique for room geometry estimation. Soo Yeon Park and Jung-Woo Choi (Elec. Eng., Korea Adv. Inst. of Sci. and Technol., KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, South Korea, [email protected]) Room geometry estimation using acoustic room impulse responses (RIRs) has been tackled in various ways. Most of them detect wall locations using the time of arrival (TOA) of echoes between multiple microphones and loudspeakers. To combine TOA information from multiple room impulse responses, echoes from the same walls should be collected and processed together. When multiple micro- phones are widely distributed in a room, however, it is hard to identify walls responsible for the generation of each echo. In this work, an iterative update algorithm is proposed for resolving the echo labeling problem with low computational complexity. Unlike conven- tional algorithms utilizing the rank property of Euclidean distance matrix, the proposed algorithm utilizes the property of convex hull formed by ellipses representing individual TOAs. The location of the reflectors are sequentially identified from common tangent lines constituting the convex hull, and the search result is iteratively updated by inspecting later echoes in time. In addition, a termination cri- terion is also developed in order to enable the geometry estimation without the prior knowledge