1999 November, VOLUME 47 NUMBER 11

CONTENT

PAPERS

Errors in MLS Measurements Caused by Time Variance in Acoustic Systems
U. Peter Svensson and Johan L. Nielsen 907

The effects of both interperiodic and intraperiodic time variance on MLS acoustical measurement
were studied using time-stretching and an analogy with delay modulation as models. Practical
results of this study show that both intra- and interperiodical time variances can be detected in a
measured impulse response, and the effects of averaging can be quantified.

New Phase-Vocoder Techniques for Real-Time Pitch Shifting, Chorusing, Harmonizing, and
Other Exotic Audio Modifications Jean Laroche and Mark Dolson 928

The phase vocoder, a well understood tool for time scaling and pitch shifting, has had improvements
proposed that reduce artifacts commonly encountered when signals are time expanded by large
factors. This paper focuses primarily on pitch­scale change of speech and audio signals. Two
alternative methods are presented which significantly reduce the computational complexity and cost,
while enabling chorusing, harmonizing, partial stretching, and frequency inversions.

ENGINEERING REPORTS

Dependence of Subject and Measurement Position in Binaural Signal Acquisition
V. Ralph Algazi, Carlos Avendano, and Dennis Thompson 937

Extensive acoustical source location measurements were performed along the ear canal of a KEMAR
mannequin and two human subjects. The goal was to present a detailed evaluation of a recording
microphone's positions along the ear canal of the head-related transfer functions (HRTFs) under
blocked and unblocked conditions. It was shown that there are conditions under which the magnitude
transfer function from the HRTF acquisition position to the eardrum is essentially independent of the
source location.

A Worst-Case Analysis for Analog-Quality (Alias-Free) Digital Dynamics Processing
Dan Mapes-Riordan 948

Digital dynamics signal processing generates significant and undesired distortion products;
these are aliases that occur below 20 kHz. To uncover the presence of these products in typical
digital audio systems, a closely spaced pair of sinusoids is slowly swept in frequency, and the aliasing
products are observed. It is suggested that there is a correlation between the amount of aliasing
distortion in digital dynamics processors and their perceived sonic qualities.

STANDARDS AND INFORMATION DOCUMENTS

DRAFT AES-6id-xxxx AES Standard for Information document for digital audio --
Personal computer audio quality measurements (insert)

AES Standards Committee News 953

Digital interfaces, audio-file transfer, IEEE 1394, microphones, forensic audio

FEATURES

17th Conference Report, Florence, Italy 962

107th Convention Report, New York 970

Exhibitors 986

Program 990

Digital Audio and the Challenge of the Internet Roger Lagadec 1013

AES News: Real-time Multichannel Audio over the Internet 1022

Education News 1023

DEPARTMENTS

Review of Acoustical Patents 959

News of the Sections 1018

Upcoming Meetings 1021

Sound Track 1025

Available Literature 1026

New Products and Developments 1028

Membership Information 1030

In Memoriam 1033

Sections Contacts Directory 1034

AES Conventions and Conferences 1040

In this issue...

Time-Variance in Acoustic Measurements

Enhanced Vocoder Techniques

Binaural Signal Acquisition

Digital Dynamics Processing Analysis

Draft Standards: Personal-computer audio measurement

Features...

17th Conference Report
Florence, Italy

107th Convention Report
New York

Audio and the Internet

Internet Real-time
Multichannel Audio

Education News

FPOFor the cover:

Volume 47 Number 1 1999 November

spine:VOLUME 47, NO. 11 1999 NOVEMBER