2007 November, Volume 55 Number 11

CONTENTS

President's Message
Bob Moses   939

Editor's Note
John Vanderkooy   940

PAPERS

The Influence of Impulse Response Length and Transition Bandwidth of Magnitude Complementary Crossovers on Perceived Sound Quality
Iva M. Salom, Dejan Z. Todorvi´c, and Ljiljana D. Mili´c   941
This study explores the degree to which the transition bandwidth and phase distortion influence the sound quality of magnitude complementary crossover filter pairs. Three sets of tests examined the perception of these two characteristics of crossovers implemented as IIR and linear phase FIR magnitude complementary pairs. IIR filter pairs are constructed as tapped cascaded interconnection of all-pass filters, and their advantages are simple realization, easily adjustable crossover frequency, and narrow transition bandwidth. Since there was no significant statistical dependency among the results of the listening tests for the used set of characteristics, mentioned IIR magnitude complementary filter pairs become an attractive choice for digital loudspeaker crossovers.

Robust and Efficient Implementation of the PEM-AFROW Algorithm for Acoustic Feedback Cancellation
Geert Rombouts, Toon van Waterschoot, and Marc Moonen   955
In public address applications in which a loudspeaker, room, microphone, and amplifier form a closed-loop system, acoustic feedback may arise when the loop gain exceeds unity at some frequencies. This is experienced as oscillation, coloration, or howling. The prediction error method adaptive filter (PEM-AFROW) algorithm is one method to reduce the likelihood of feedback. A controller that uses a model of the room impulse response is added to the signal loop to remove the portion of the microphone signal that stems from the loudspeaker. Several techniques can be added to the adaptation algorithm to achieve robustness without excessive complexity.

Beat Deviation for Tempo Estimation Algorithms
David Rossiter, Raymond Tsang, and Richard H. Y. So   967
In automatic music recognition and classification systems, tempo identification is one of the tools used. However, without first understanding the normal variance of the beat in music, such algorithms may inaccurately determine tempo. This study analyzed the tapping sequence of 5 musicians for 50 music recordings to determine the statistics of natural beat variation. Permissible deviations were empirically observed. The results should improve the utility of algorithms that employ tempo identification as one of the decision components.

ENGINEERING REPORTS

Subjective and Objective Evaluation of the Optimal Source Distribution for Virtual Acoustic Imaging
Takashi Takeuchi and Philip A. Nelson   981
Optimal Source Distribution (OSD) overcomes a number of problems associated with binaural synthesis with loudspeakers, such as a loss of dynamic range and a high sensitivity to small errors. A practical realization of OSD uses discrete transducers, which approximates the loudspeaker with variable position as a function of frequency. In this way, the cross-talk cancellation process is optimized for entire audible frequency regions. This approach dramatically improves the dynamic range and other aspects of performance. Subjective evaluations confirmed the advantages over sound localization.

STANDARDS AND INFORMATION DOCUMENTS

AES Standards Committee News   998
Storage and handling of media; digital library and archive systems; forensic audio; digital audio measurements; digital input/output interfacing; audio file transfer and exchange

FEATURES

1st Latin American Conference Report, Buenos Aires   1002
Digital Broadcasting in the IP Age   1021
33rd Conference, Denver, Call for Papers   1047

TECHNICAL COUNCIL REPORTS

Technical Committee Reports: Emerging Trends in Technology   1004

DEPARTMENTS

News of the Sections   1025
Sound Track   1035
New Products and Developments   1036
Upcoming Meetings   1037
Available Literature   1038
Membership Information   1041
Advertiser Internet Directory   1045
AES Annual Report   1046
Sections Contacts Directory   1048
AES Conventions and Conferences   1056

FPO For the cover:

2007 November, Volume 55 Number 11

spine: 2007 November, Volume 55 Number 11