| 2004 December, Volume 52 Number 12 |
CONTENT
PAPERS
Subtractive and Nonsubstractive Dithering: A Mathematical Comparison
Robert A. Wannamaker 1211
The relative advantages and disadvantages of subtractive and nonsubtractive dithering are explored from a mathematical perspective. Subtractively dithered systems can yield quantization errors that are statistically independent of the input signal, but that require the dither signal be either transmitted or reconstructed at the receiver. In contrast, nonsubtractively dithered systems avoid this drawback but increase the level of noise at the output and can only render a specified number of statistical error moments independent of the system input. Nonetheless, appropriately chosen nonsubtractive dither signals prove suitable for audio and many other applications. The treatment presented extends to include new results regarding the use of spectrally colored dither signals in systems with and without noise-shaping error feedback.
Measuring and Predicting the Perceived Quality of Music and Speech Subjected to Combined Linear and Nonlinear Distortion
Brian C. J. Moore, Chin-Tuan Tan, Nick Zacharov, and Ville-Veikko Mattila 1228
A new model is presented for predicting the perceived quality of audio signals subjected to both linear and nonlinear distortion. Earlier research produced metrics for predicting the effects of linear distortion (frequency response irregularity) and nonlinear distortion (production of spurious spectral components). The new model, which includes both metrics, provides predictions that correlate highly with results of subjective tests: correlations were 0.90 for music and 0.85 for speech.
Circular Recital Hall Design Considering Source Directivity
Wei-Hwa Chiang, Yi-Nuo Chao, Jow-Yeh Lee, and Hui-Ping Wu 1245
During the remodeling of the Carrie Chang Music Hall, early reflections were incorporated into the acoustical design in order to compensate for the loss of high frequencies in those seats that were off axis. The design concentrated on several issues: changes in tone quality resulting from source directivity, sound focusing from curved surfaces, and coloration due to discrete early reflections. Computer and scale models allowed for acoustic analysis during successive design phases.
ENGINEERING REPORTS
Study of the Directional Characteristics of a Piston Mounted on a Surface of Zero Acoustic Impedance
José Luis Barros, Jorge Cárdenas, and Jorge Sommerhoff 1254
The surface impedance of a loudspeaker baffle strongly influences the directionality of the radiation pattern. By contrasting the radiation pattern of a vibrating piston mounted in a surface having infinite impedance with one having zero impedance, the importance of surface impedance is clearly demonstrated. Because energy cannot flow horizontally in a zero impedance surface, energy is concentrated in the axial direction. A two-dimensional model produced results that were consistent with those measured in the laboratory.
LETTERS TO THE EDITOR
Comments on "Coding for High-Resolution Audio Systems"
David Moran, Roy Allison, and E. Brad Meyer 1259
David Hadaway 1259
Author's Reply
J. Robert Stuart 1259
STANDARDS AND INFORMATION DOCUMENTS
Special Feature: Real-World Applications of ATM Networking for Professional Audio Using the AES47 Standard 1265
David Errock
FEATURES
The World of Digital Radio 1272
Call for Nominations for Board of Governors 1290
Call for Awards Nominations 1291
12th Regional Convention, Tokyo, Call for Papers 1299
27th Conference, Copenhagen, Call for Papers 1300
Bylaws: Audio Engineering Society, Inc. 1301
Index to Volume 52 1305
DEPARTMENTS
Reviews of Acoustical Patents 1262
News of the Sections 1280
Sound Track 1286
New Products and Developments 1287
Available Literature 1289
Upcoming Meetings 1289
Membership Information 1292
Advertiser Internet Directory 1296
In Memoriam 1297
Sections Contacts Directory 1321
AES Conventions and Conferences 1328
FPO For the cover:
2004 December, Volume 52 Number 12
spine: 2004 December, Volume 52 Number 12