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Journal of the Audio Engineering Society

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2009 December - Volume 57 Number 12

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Papers

Estimating the Velocity Profile and Acoustical Quantities of a Harmonically Vibrating Loudspeaker Membrane from On-Axis Pressure Data

Authors: Aarts, Ronald M.; Janssen, Augustus J. E. M.

The velocity profiles of rigid pistons, supported radiators, clamped radiators, Gaussian radiators, and real loudspeaker drivers can be approximated using only a few terms of their Zernike expansions. The computed profile allows for the extrapolation of far-field pressure data, including off-axis behavior without requiring the use of anechoic rooms. The authors explore a method to perform forward and inverse sound pressure computations for circular radiators with nonuniform velocity profiles. Acoustic parameters of a harmonically excited resilient, flat, circular loudspeaker in an infinite baffle can thus be computed.

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Psychoacoustic Evaluation of Systems for Delivering Spatialized Augmented-Reality Audio

Authors: Martin, Aengus; Jin, Craig; Schaik, André van

Spatialized augmented-reality audio systems superimpose virtual sound sources onto sounds from a real acoustic environment. Applications include assistance for visually impaired users, guidance systems, teleconferencing, attention-focusing systems, and electronic games. In the proposed system, acoustically transparent earpieces are used to allow environmental sounds to be heard directly while the virtual reality is created electronically. The results show that the listener can localize virtual sound sources as accurately as when using earphones, which are standard for virtual auditory space presentation, while there is only minor degradation in his ability to localize real sound sources.

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Ensemble Hand-Clapping Experiments under the Influence of Delay and Various Acoustic Environments

Authors: Farner, Snorre; Solvang, Audun; Sæbo, Asbjørn; Svensson, U. Peter

With ensembles composed of musicians connected over large distances via the Internet, the issue of sound delay becomes very important. This study explores the effect of delay on tempo change, imprecision, leader–follower strategy, and quality. Eleven pairs of musically experienced subjects clapped a simple complementary rhythmic pattern together for about 15 seconds while the delay was varied from 6 to 68 ms. Acceptable delay thresholds were empirically determined.

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Engineering reports

FlexSM: A Flexible Sinusoidal Modeling System

Authors: Nunes, Leonardo O.; Esquef, Paulo A. A.; Biscainho, Luiz W. P.

A system, called FlexSM, is proposed, which is a unified yet flexible platform for developing, testing, and comparing existing as well as new algorithms for sinusoidal analysis of audio. FlexSM, which is implemented in Matlab, offers a graphical user interface and a report generator to aid system configuration and visual assessment of the results.

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Standards and Information Documents

AES Standards Committee News

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Features

Class D Power Amplification

Authors: Rumsey, Francis

[Feature] Class D power amplifiers are rapidly becoming the technology of choice for audio products. Integration of these amplifiers in CMOS (complementary metal oxide semiconductor) designs for portable devices requires careful treatment if audio power output is to be maximized for minimal power consumption, while at the same time ensuring low electromagnetic interference and protection of loudspeakers. Papers from the 37th International Conference dealing with these themes are summarized, showing that effective solutions can be developed.

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