VOLUME 45 NUMBER 5 1997 May

CONTENT

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President's Message - The AES: The Voice of Technical Leadership
Elizabeth A. Cohen 315

PAPERS

Hybrid Sampling-Wavetable Synthesis with Genetic Algorithms

Jennifer Yuen and Andrew Horner 316

A combination of hybrid sampling and wavetable synthesis for matching acoustic instruments is demonstrated using genetic algorithm optimization. Tone sampling is used for the critical attack portion and wavetable synthesis is used to match the more gradually changing sustain and decay. A hybrid sampling wavetable performs a smooth crossfade transition. This method has been used to synthesize piano, harp, glockenspiel, and temple block tones.

Measurement of Directional Scattering Coefficients Using Near-Field Acoustic Holography and Spatial Transformation of Sound Fields

Mendel Kleiner, Hans Gustafsson, and Joakim Backman 331

Near-field holography is used to measure the sound field above the surface of an acoustical scatterer. The scattered sound field is then spatially transformed to the desired distance and angle; the angle corresponds to a specific angle relative to the surface normal. This method can predict the sound field at close distances to the scattering object, while the data storage requirement is smaller than conventional polar response measurements.

Fundamentals of Diffraction

J. R. Wright 347

Basic theoretical and practical analysis has been performed to clarify the physical attributes of diffraction. Using finite element analysis (FEA) simple measurements corroborate the evidence of this study. Several methods are used to illustrate the diffraction effect. The author suggests that further detailed physical understanding of the diffraction mechanism is still desired.

ENGINEERING REPORTS

Optimizing the Voice-Coil-Airgap Geometry for Maximum Loudspeaker Motor Strength
Carlo Zuccatti 357

The strength of a loudspeaker motor can be optimized by designing a voice coil that overhangs slightly the magnetic field gap. The stray field at the gap's edge can be engaged additionally toincrease the overall strength of the motor force.

STANDARDS AND INFORMATION DOCUMENTS

AES28-1997

AES standard for audio preservation and restoration - Method for estimating life expectancy of compact discs (CD-ROM), based on effects of temperature and relative humidity 360

AES Standards Committee News 379

Internet subcommittee formation; SC-02, SC-04, and SC-05 meeting reports

FEATURES

102nd Convention Report 386

Exhibitors 398

Program 4028th Regional Convention, Tokyo, Japan: Preview (insert)