Journal of the Audio Engineering Society

2003 July/August - Volume 51 Number 7/8


Demystifing Audio Metadata

Authors: Harris, Steven

[feature article] Metadata is one of those words that gets bandied about a lot at conferences and by various groups, particularly within broadcasting and digital library circles. But it is also cropping up in numerous other fields, such as digital rights management, content delivery, business models for the music industry, and so forth. The field is rife with acronyms and arcane terms that leave the uninitiated baffled, particularly because metadata is really more concerned with information systems than it is with audio. This article aims to demystify metadata for audio professionals and to explain some of the key terms and developments. It is based partly on the AES Metadata Symposium that was run in conjunction with the 112th Convention in Munich last year, but it goes back to basics in order to make the topic approachable for the relative novice.

Author's Reply to Letter to the editor

Comments on `Deciphering an Enigma`

Authors: Sankiewicz, Marianna; Budzynski, Gustaw

Letter to the editor

A differential pressure synthesis (DPS) method is proposed which estimates the free-field acoustic pressure on the boundary of an object from its geometry by precalculating a database of pressure changes caused by introducing orthogonal shape deformations to a template shape. Pressures are synthesized using DPS for a two-dimensional shape and a three-dimensional KEMAR head model. The accuracy of pressure estimates compares favorably with the boundary-element method computation provided that shape deformations are moderate in relation to acoustic wavelength.

Psychoacoustic Investigations On Sound-Source Occlusion

Authors: Farag, Hania; Blauert, Jens; Abdel Alim, Onsy

Efficient simulation of sound-source occlusion is needed, for example, in auditory virtual environments, and remains an interesting and at present not widely researched topic. In order to achieve plausible and efficient simulation, the changes in psychoacoustical parameters accompanying the perception of sound-source occlusion have to be identified and understood. The impact of occlusion on the localization of auditory events is investigated with the aid of listening tests. Rectangular wood plates of different dimensions are used as occluders. A noticeable shift in the location of the auditory events is observed. The results can be explained on grounds of the precedence effect.

Direct-Radiator Loudspeaker Systems with High Bl

Authors: Vanderkooy, John; Boers, Paul M.; Aarts, Ronald M.

In an extension of an earlier paper by the authors additional consequences of a dramatic increase in the motor strength Bl of a driver are shown. Not only is the efficiency of the loudspeaker and amplifier greatly increased, but high Bl values have a positive influence on other aspects of loudspeaker systems. Box volume can be reduced significantly and other parameters can be altered. A prototype driver unit is studied, which performs well in a small sealed box. Vented systems do not benefit as much from high Bl.

The full-sphere sound radiation pattern of the constant-beamwidth transducer circular-wedge curved-line loudspeaker array exhibits a three-dimensional petal or eyeshaped sound radiation pattern that stays surprisingly uniform with frequency. Oriented vertically, it not only exhibits the expected uniform control of vertical coverage, but also provides significant coverage control horizontally. The horizontal control is provided by a vertical coverage that decreases smoothly as a function of the horizontal off-axis angle and reaches a minimum at right angles to the primary listening axis. This is in contrast to a straight-line array, which exhibits a three-dimensional sound field that is axially symmetric about its vertical axis and exhibits only minimal directivity in the horizontal plane due to the inherent directional characteristics of each of the sources that make up the array.

Engineering reports

The Differential Pressure Synthesis Method for Efficient Acoustic Pressure Estimation

Standards and Information Documents

AES47-2002 AES standard for digital audio-Digital input-output interfacing-Transmission of digital audio over asynchronous transfer mode (ATM) networks

AES-R4-2002 AES standards project report-Guidelines for AES standard for digital audio- Digital input-output interfacing-Transmission of digital audio over asynchronous transfer mode (ATM) networks, AES47

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