2007 April, Volume 55 Number 4

CONTENTS

PAPERS

Blind Cancellation of Stereo-Base Widening
Erik van de Ven, Ronald M. Aarts, and Piet C. W. Sommen   227
Depending on the application, signal processing in audio reproduction equipment is often used to widen the perceived image, especially when the listener is relatively far from the sound source or when the stereo loudspeakers are close together. However, if the stereo signal has already been widened, a second widening can produce severe spatial degradation and coloration. For this reason, an algorithm that determines if the signal has already been widened allows for a conditional widening only if the signal has not been so processed. A reliable model for widening based on the statistics of phase difference between the stereo pair is presented and validated.

Examination of Multichannel Sound-Field Recomposition Utilizing Frequency-Dependent Interaural Cross Correlation (FIACC)
Teruo Muraoka and Tomoaki Nakazato   236
A frequency-dependent interaural cross correlation (FIACC) metric was used to evaluate the degree to which a variety of loudspeaker configurations could adequately reproduce the sound field of a large space. By comparing the metric of a real and reproduced space using a dummy head, an objective measure of each configuration could be established. The five-channel system configured according to the ITU recommendation BS.775-1 was shown to be optimum.

Derivation of a Transfer Function for Imaging Polarimetry Used in Magneto-Optical Investigations of Audio Tapes in Authenticity Investigations
Jos Bouten, Mariska van Rijsbergen, and Simon Donkers   257
Ferrimagnetic garnet films, known as Faraday crystals, offer a nondestructive means for forensic authentication of tape recordings. But in order to replace the more familiar pictures using ferrofluids, which may alter the tape's magnetism, a theoretical explanation for the physics of this new technique must be established. What are the pictures actually showing? A theoretical model, including a practical transfer function, establishes the relationship between the magnetic distribution and the resulting visualization.

DSP Techniques for Determining "Wow" Distortion
Andrzej Czyzewski, Andrej Ciarkowski, Andrzej Kaczmarek, Jozef Kotus, Maciej Kulesza, and Przemek Maziewski   266
Given the artistic value of archived analog recordings, there is strong desire to use modern signal processing techniques to remove wow degradations created by variations in speed. A new set of algorithms is proposed to model speed variations by tracking the frequency of incidental pilot tones, such as hum and bias frequency, and by using an adaptive analysis of the center of gravity of the spectrum of the distorted signal. A semiautomated adaptive approach, with a human operator making critical choices, improves performance.

STANDARDS AND INFORMATION DOCUMENTS

AES Standards Committee News   285
Membership; digital audio interfaces, AES3 implementation guidelines; digital audio measurements, jitter performance

FEATURES

31st Conference Preview, London   290
     Calendar   292
     Program   293
     Registration Form   300
Audio for Mobile and Handheld Devices   301

DEPARTMENTS

Reviews of Acoustical Patents   287
News of the Sections   305
Sound Track   310
New Products and Developments   313
Available Literature   314
Upcoming Meetings   315
Membership Information   316
Advertiser Internet Directory   317
In Memoriam   319
Sections Contacts Directory   320
AES Conventions and Conferences   328

FPO For the cover:

2007 April, Volume 55 Number 4

spine: 2007 April, Volume 55 Number 4