2003 September, Volume 51 Number 9

CONTENT

In Memoriam: Patricia Macdonald
Roger K. Furness   779

PAPERS

Effects of Down-Mix Algorithms on Quality of Surround Sound
Slawomir K. Zielinski, Francis Rumsey, and Søren Bech   780
When channel limitations prevent the transmission of a full 5.1 surround mix, there are many options for converting to a lesser number of channels using down mixing. Listeners were asked to evaluate eight different algorithms from two listening positions in terms of preferences rather than quality. Unfortunately, different audio cases produced variations in the conclusion about optimum. The presence of a video picture influenced the experience of reduced audio channels.

A Study on Head-Shape Simplification Using Spherical Harmonics for HRTF Computation at Low Frequencies
Yufei Tao, Anthony I. Tew, and Stuart J. Porter   799
Using a simplified shape for the human head in computing head-related transfer functions (HRTFs) produces errors in the calculated pressures on the surface. A model of a head can be represented as a series of spherical harmonics. This study computes the errors in acoustic pressure that result from truncating the series, which corresponds to low-pass shape filtering. These shape errors follow the corresponding pressure errors for frequencies below 3 kHz. Harmonics to order 11 are sufficient for the low frequencies representation of a head. Beyond order 14 there is no additional improvement.

Differences in Performance and Preference of Trained versus Untrained Listeners in Loudspeaker Tests: A Case Study
Sean E. Olive   806
The audio industry makes many assumptions about the appropriateness of various quality testing methods, but there have not been any significant studies to validate these assumptions. The choices are reduced to using trained listeners, who are efficient and discriminating, or untrained listeners, who are more representative of the user population. This 18-month study shows that trained listeners produce the same conclusion as 268 untrained listeners when evaluating loudspeakers.

Objective Measures of Listener Envelopment in Multichannel Surround Systems
Gilbert A. Soulodre, Michel C. Lavoie, and Scott G. Norcross   826
Predicting the degree of listener envelopment is more complex than the traditional measures of lateral energy after the first 80 ms. This detailed study shows that the transition threshold between early and late energy is frequency-dependent. In addition, the loudness of the lateral energy is equally important. A new objective measure is proposed with a very high correlation between perceived envelopment and the calculated metric.

LETTERS TO THE EDITOR

"More Comments on President's Message and Comments"
John Woodgate   841

STANDARDS AND INFORMATION DOCUMENTS

AES Standards Committee News   842
Sampling frequencies; digital audio synchronization; preservation and restoration of recordings; loudspeaker modeling and measurement

FEATURES

23rd Conference Report, Copenhagen   846
Digital Rights Management   855
25th Conference, London, Call for Papers   871

DEPARTMENTS

News of the Sections   861
Sound Track   865
New Products and Developments   867
Upcoming Meetings   868
Available Literature   869
Membership Information   872
Advertiser Internet Directory   873
Sections Contacts Directory   874
AES Conventions and Conferences   880

FPO For the cover:

2003 September, Volume 51 Number 9

spine: 2003 September, Volume 51 Number 9