VOLUME 45 NUMBER 4 1997 April

President's Message Conference, Copyright: seeing and hearing

Elizabeth A. Cohen 211

PAPERS

Psychoacoustically Optimal Sigma-Delta Modulation

Chris Dunn and Mark Sandler 212

Noise characteristics of high-resolution sigma-delta modulation audio converters have been investigated by the authors and they have identified two desirable attributes: 1) the noise floor should be free of idle tones, and 2) other low-level artifacts in the noise floor should be minimally audible. Dither can be used to linearize sigma-delta modulators, while careful choice of noise-shaping zero locations can affect psychoacoustically appropriate shaping of the modulator noise floor.

A Model for the Prediction of Thresholds, Loudness, and Partial Loudness

Brian C. J. Moore, Brian R. Glasberg, and Thomas Baer 224

A loudness model utilizing two filters is presented that emulates the outer and middle ear. This system transforms the excitation pattern to a specific loudness pattern. It accounts for the threshold and loudness of complex sounds as a function of bandwidth. This model correctly predicts the relationship between monaural and binaural thresholds and loudness.

Wavetable Modeling of Muted Brass Tones

Andrew Horner 241

Wavetable matching is used to model open tones for brass instruments with an additional wavetable that matches the muted tones. This method is more accurate than those employing simple filter characteristics, since it can also simulate partially muted and dynamic muted tones. Spectrograms that illustrate the results are included for various mutes on the trumpet, trombone, and French horn.

Sound Absorption of Gypsum Board Cavity Walls

J. S. Bradley 253

A calculation model was developed to predict the sound absorption of several cavity-type gypsum-board walls that accurately fits the measured data. This model can be used to predict both low- and high-frequency losses effectively in hollow gypsum-board wall construction. It is a valuable tool in designing walls with a specified minimal amount of low-frequency absorption.

STANDARDS AND INFORMATION DOCUMENTS

AES11-1997

AES recommended practice for digital audio engineering - Synchronization of digital audio equipment in studio operations 260

AES Standards Committee News 270

Scopes of subcommittees and working groups; symbols standard

FEATURES

AES 14th International Conference, Seattle, Washington: "internetaudio.aes.org" 276

Calendar 277

Program 278

Updates and Corrections to the 1996/1997 AES International Sections Directory 287