2003 May, Vol 51 Number 5

CONTENT

PAPERS

Assessment of Voice-Coil Peak Displacement Xmax
Wolfgang Klippel   307
Peak voice-coil displacement is an important parameter for specifying the maximum acoustic output at low frequencies. However, the absence of a single definition for distortion produces ambiguous results that can not be easily compared. For example, choices include distortion in the voice-coil current or cone displacement. Alternatively, a parametric method that provides more detailed information about the cause of the distortion is proposed. A comparison between performance-based and parameter-based techniques illustrates the advantages and disadvantages.

Modal Equalization of Loudspeaker-Room Responses at Low Frequencies
Aki Mäkivirta, Poju Antsalo, Matti Karjalainen, and Vesa Välimäki   324
Compensation for the dominant low-frequency modes in small rooms traditionally uses equalization filters in cascade with the main sound source. In an alternative implementation, multiple sources produce better modal cancellation when traditional methods fail. Case studies show that the extra degrees of spatial freedom afforded by the additional sources make the system more robust. Modal equalization is a design option when the modal density is not high and when the modes are low frequency. It can also be combined with cascade equalization.

A Low-Cost Intensity Probe
R. Raangs, W. F. Druyvesteyn, and H.-E. de Bree   344
Unlike ordinary microphones, a sound intensity probe measures the energy flow as a vector direction. It can be computed as the product of scalar pressure and vector velocity. In a conventional probe, velocity is computed as the difference in pressure at a small fixed distance. The authors propose a novel means of directly measuring velocity using the temperature difference between two heated wires mounted in a microminiaturized substrate. When combined with a standard pressure sensor, the probe measures sound intensity over the full spectrum at a single point in space. The paper provides examples of several methods for calibration of the particle velocity sensor used, such as in a standing-wave tube, reverberant room, anechoic space, and reverberation room. Two examples of sound-intensity measurements are provided and are compared with a conventional sound intensity probe.

ENGINEERING REPORTS

Industry Evaluation of In-Band On-Channel Digital Audio Broadcast Systems
David Wilson   358
The proposed techniques for terrestrial broadcasting of digital audio from iBiquity were evaluated using standard metrics: coverage, compatibility, interference, and quality. In order to maintain compatibility with existing AM and FM analog broadcasting, digital information was added as low-amplitude side bands around the main analog spectrum. While the proposed solution achieves the desired goal of preserving the existing competitive balance between radio broadcasters, there is an additional interference outside the protected geographic region. Subjective listening tests confirmed that digital audio improved the quality even at reduced bit rates.

STANDARDS AND INFORMATION DOCUMENTS

AES46-2002 AES standard for network and file transfer of audio - Audio-file transfer and exchange - Radio traffic audio delivery extension to the broadcast WAVE file format   369
AES Standards Committee News   384
Julian Dunn; resonance of loudspeaker cones

FEATURES

114th Convention Report, Amsterdam   386
     Exhibitors   402
     Program   405
TECHNICAL COUNCIL REPORTS
Technical Committee Reports: Emerging Trends in Technology   442

DEPARTMENTS

News of the Sections   452
Upcoming Meetings   458
Advertiser Internet Directory   459
Sound Track   460
New Products and Developments   460
Available Literature   461
Membership Information   463
In Memoriam   465
Sections Contacts Directory   466
AES Conventions and Conferences   472

FPO For the cover:

2003 May, Vol 51 Number 5

spine: 2003 May, Vol 51 Number 5