|1996 JULY/AUGUST, VOLUME 44 NUMBER 7/8|
Frequency and Angular Resolution for Measuring, Presenting, and Predicting Loudspeaker Polar Data
Felicity Seidel and Henrik Staffeldt p. 555
The relationships between measurement resolution and the accuracy of presented or predicted polar and frequency responses from single or arrayed loudspeakers are presented. Only direct loudspeaker- generated sound fields are addressed. Observations are made of current, commonly used measurement techniques, which can yield results with significant errors. The discussion includes the possible need to reconsider how loudspeakers should be measured, taking into account the increasing improvements in measuring equipment, data processing systems, and storage techniques.
A Model of Nonlinear Wave Propagation in Horns
Keith R. Holland and Christopher L. Morfey p. 569
Sound propagation modeling in acoustic horns at high levels is analyzed. This model can predict the degree of nonlinear waveform distortion associated with propagation in the horn of large amplitude waves. The predicted output sound field can then be corrected for nonlinear distortion by appropriately predistorting the input signal, using the modeling-determined data.
Discrete Summation Synthesis of Musical Instrument Tones Using Genetic Algorithms
San-kuen Chan and Andrew Horner p. 581
An automated genetic algorithm method determines discrete synthesis parameters for matching an arbitrary harmonic instrument tone. This work synthesizes the spectra of the trombone, English horn, and the Chinese pipa. This unique technique uses discrete summation matching, which requires less computer memory compared to wavetable matching. Although the relative error using a wavetable is always smaller than that of discrete summation, it is a good alternative choice when wavetable memory is limited since it requires only a single sine wave.
Improving Audio Codecs by Noise Substitution
Donald Schulz 593
Separate coding of noise and signal components is proposed for greater data reduction. Combinations of adaptive transform coding and adaptive subband coding using time and frequency domains in subbands distinguish between tonal and noisy audio components. Listening tests have confirmed the superiority of combined algorithms for a variety of different music signals, while the data rate was decreased by approximately 20%.
STANDARDS AND INFORMATION DOCUMENTS
AES Standards Committee News p. 599
AES3 interface meetings; loudspeakers and microphones
DRAFT AES-5id-xxxx, AES information document for Room acoustics and sound reinforcement system modeling - Loudspeaker modeling and measurement - Frequency and angular resolution for measuring, presenting and predicting loudspeaker polar data (insert)
100th Convention Report p. 610
Exhibitors p. 624
Program p. 627
102nd Convention, Munich, Germany: Call for Papers p. 673
Review of Acoustical Patents p. 603
News of the Sections p. 654
Upcoming Meetings p. 656
Sound Track p. 657
New Products and Developments p. 658
Available Literature p. 662
Membership Information p. 664
In Memoriam p. 669
Sections Contacts Directory p. 676
AES Conventions and Conferences p. 680