2002 September, Vol 50 Number 9

CONTENT

PAPERS

Spatial Quality Evaluation for Reproduced Sound: Terminology, Meaning, and a Scene-Based Paradigm
Francis Rumsey   651
Improving the quality of spatial reproduction suffers because of an incomplete definition of the subjective attributes that contribute to the experience of space. Moreover, the lexicon of spatial concepts is often ambiguous and ill defined. This review of existing standards and research highlights the problem of extending controlled laboratory results to real applications of sound reproduction, especially when different goals, such as evaluating equipment versus modeling human perception, are involved.

Describing Telephone Speech Codec Quality Degradations by Means of Impairment Factors
Sebastian Möller and Jens Berger   667
Predicting the quality of a telephone channel with multiple sources of degradations from a variety of codecs is a labor-intensive activity that must be repeated for each condition. The authors propose a perceptually based model that produces a single equipment impairment index as a way to approximate the degradation contributed by a particular device. Preliminary results suggest that the proposed algorithm, based on auditory tests, provides insight into the expected results.

Low-Crest-Factor Multitone Test Signals for Audio Testing
Alexander Potchinkov   681
Test signals composed of a large number of discrete frequencies offer the advantage of high-speed measurements and the ability to simulate the spectrum of natural audio under controlled conditions. However, selecting the phase relationship to minimize the crest factor becomes a special problem. Minimizing the crest factor increases the signal power for a fixed clipping level. This paper shows that ad hoc schemes are useful but often inferior to a formal optimization, and that they should not be used if enough compute time is available for a theoretical optimization.

ENGINEERING REPORTS

About the 10-dB Switch of a Condenser Microphone in Audio Frequency Circuits
Holger Pastillé and Martin Ochmann   695
Because high sound levels can overload the input preamplifier of a condenser microphone, one of two techniques is typically used to reduce the level: switching a parallel capacitor across the microphone or reducing the polarizing voltage. Both techniques reduce the signal level but with very different effects on nonlinearity. This paper explores both the mathematical and practical implications of level reduction, with a warning to users faced with an overload condition.

STANDARDS AND INFORMATION DOCUMENTS

AES Standards Committee News   703
Internet communications update; synchronization; forensic audio; microphone measurement; listening tests; audio connections
Survey: Fiber Optic Connectors   insert

FEATURES

21st Conference Report, St. Petersburg   710
23rd Conference, Copenhagen, Call for Papers   737
24th Conference, Banff, Call for Contributions   738

DEPARTMENTS

Review of Acoustical Patents   708
News of the Sections   718
Sound Track   725
Upcoming Meetings   726
New Products and Developments   727
Available Literature   731
Membership Information   732
Advertiser Internet Directory   734
In Memoriam   736
AES Special Publications   741
Sections Contacts Directory   746
AES Conventions and Conferences   752

FPO For the cover:

2002 September, Vol 50 Number 9

spine: 2002 September, Vol 50 Number 9