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Journal of the Audio Engineering Society

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2011 December - Volume 59 Number 12

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Papers

Interactive Teleconferencing Combining Spatial Audio Object Coding and DirAC Technology

Authors: Herre, Jürgen; Falch, Cornelia; Mahane, Dirk; Del Galdo, Giovanni; Kallinger, Markus; Thiergart, Oliver

In teleconferencing applications with multiple participants, it would be desirable to create the perception of a real meeting with each speaker in a specific perceived location. This paper describes how Directional Audio Coding (DirAC) can be used as a front end to MPEG Spatial Audio Object Coding (SAOC) to achieve that goal. A novel parameter transcoder provides an efficient way of combining the two technologies. Reproduction of the virtual environment, where each talker exists in a virtual location, can be achieved using headphones or loudspeakers. Subjective tests on different simple and optimized versions were performed, many of which were rated as “good” on the MUSHRA scale.

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Sparse Frequency-Domain Reverberator

Authors: Vilkamo, Juha; Neugebauer, Bernhard; Plogsties, Jan

There are many topologies for implementing the late part of artificial reverberation, each of which is a unique trade-off among perceived quality, computational cost, and parameter flexibility. A new approach, which assumes that the late reverberation can be described as a stochastic process, applies the reverberation in frequency bands using a combination of a feedback loop and an efficient sparse decorrelator. Listening tests with ten experts confirmed that the new reverberator topology has a perceived quality that was mostly equivalent to the idealized reverberation using decaying Gaussian noise response in frequency bands.

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A Diffractive Study on the Relation between Finite Baffle and Loudspeaker Measurement

Authors: Le, Yi; Shen, Yong; Xia, Jie

Measuring the frequency response of a driver mounted in an idealized infinite baffle is desirable even though the IEC specifies a finite baffle with fixed dimensions. Finite baffles confound direct radiation with diffracted radiation. Based on quantitative computations using the extended Boit-Tolstoy-Medwin technique, a correction process compensates the measured response with a finite baffle to the result that would be obtained with an ideal infinite baffle. Experimental results show the validity of the approach.

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Impulse Response Measurement of Nonlinear Systems: Properties of Existing Techniques and Wide Noise Sequences

Authors: Kemp, Jonathan; Primack, Harel

Methods for measuring impulse responses have problems when the system under test contains elements that are nonlinear. Before exploring a new approach to the problem, the authors explain the effects of nonlinearities on traditional impulse response techniques. They show how wide maximum-length sequences have advantages over existing techniques for measuring the linear component of the response. Then they illustrate how these advantages can be applied to multiple noise sequence measurements to measure nonlinear behavior using the diagonal Volterra series expansion of the impulse response of general nonlinear systems. This approach better characterizes the system being measured.

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Standards and Information Documents

AES Standards Committee News

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Features

Live Sound: Things to Get Right

Authors: Rumsey, Francis

[Feature] Live sound featured large in the technical program of the 131st Convention, held in October in New York, with a series of workshops organized by Henry Cohen and Mac Kerr. Although wireless microphone issues took up quite a lot of the sessions, owing to the changes taking place in that field, this article concentrates on some of the other areas of live sound that we have not covered as much in the past. It includes practical tips from a workshop entitled “Ten Things to Get Right,” as well as the use of subwoofer arrays and beamsteering.

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