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Journal of the Audio Engineering Society

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2002 October - Volume 50 Number 10

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Papers

Crossover Systems in Digital Loudspeakers

Authors: Busbridge, Simon C.; Huang, Yaxiong; Fryer, Peter A.

A digital loudspeaker is one that does not contain any form of embedded digital-to-analog converter. From a consideration of the mathematical operations describing the digital-to-analog conversion process in a digital loudspeaker, it is concluded that the use of N identical analog filters (where N is the number of bits) filtering each bit driver separately offers a practical alternative to digital signal processing. The implementation of a multiple-driver multiple-voice-coil digital loudspeaker is described. The effect of component tolerances in the crossover and compatibility with the requirements of the current drive are evaluated. The interactions between motion emf, driving current, and mutual coupling emfs are considered. It is concluded that this method of crossover implementation is both viable and achievable.

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Improved Microphone Array Configurations for Auralization of Sound Fields by Wave-Field Synthesis

Authors: Hulsebos, Edo; de Vries, Diemer; Bourdillat, Emmanuelle

In order to correctly reproduce ( "auralize" ) the acoustic wave field in a hall through a wave-field synthesis (WFS) system, impulse responses are nowadays measured along arrays of microphone positions. Three array configurations are considered linear, cross, and circular. The linear and cross array configurations both have strong limitations, most of which can be avoided by using circular arrays. Auralization techniques are explained for all types of arrays. For the circular array configuration the connection between circular holophony, high-order incoming and outgoing ambisonics, and plane-wave decomposition for a sound field will be established and used as a tool for auralization.

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Perceptual Evaluation of Speech Quality (PESQ) The New ITU Standard for End-to-End Speech Quality Assessment Part II: Psychoacoustic Model

Authors: Beerends, John G.; Hekstra, Andries P.; Rix, Antony W.; Hollier, Michael P.

A new model for the perceptual evaluation of speech quality (PESQ) was recently standardized by the International Telecommunications Union as Recommendation P.862. Unlike previous codec assessment models, such as PSQM and MNB (ITU-T P.861), PESQ is able to predict subjective quality with good correlation in a very wide range of conditions, which may include coding distortions, errors, noise, filtering, delay, and variable delay. The psychoacoustic model used in PESQ is introduced. Part I describes the time-delay identification technique that is used in combination with the PESQ psychoacoustic model to predict the end-to-end perceived speech quality.

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Perceptual Evaluation of Speech Quality (PESQ) The New ITU Standard for End-to-End Speech Quality Assessment Part I--Time-Delay Compensation

Authors: Rix, Antony W.; Hollier, Michael P.; Hekstra, Andries P.; Beerends, John G.

A new model for the perceptual evaluation of speech quality (PESQ) was recently standardized by the International Telecommunications Union as Recommendation P.862. Unlike previous codec assessment models, such as PSQM and MNB (ITU-T P.861), PESQ is able to predict subjective quality with good correlation in a very wide range of conditions, which may include coding distortions, errors, noise, filtering, delay, and variable delay. In Part I time-delay identification techniques are introduced and some causes of variable delay are outlined before the processes that are integrated into PESQ and specified in P.862 are described. More information on the structure of PESQ as well as performance results will be given in Part II.

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