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Journal of the AES


2003 April - Volume 51 Number 4

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Papers

PAPERS
The Bidirectional Microphone: A Forgotten Patriarch (PDF-837KB)  
Ron Streicher and Wes Dooley    211
After reviewing the history and general issues of microphones and their sensitivity patterns, the authors focus on a pure bidirectional microphone. It is the most difficult to use. Specifically, its major virtue is the ability to place nulls at orientations to suppress unwanted sound pickup. All microphone patterns can be described in terms of a combination of an omnidirectional and figure-of-eight pattern. Many common sense rules are discussed to avoid accidental destruction of microphones' ribbons.  
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Efficient Tempo and Beat Tracking in Audio Recordings (PDF-124K)  
Jean Laroche    226
Automatically measuring musical beat is useful in sound analysis, crossfade synchronization, and audio editing. A proposed off-line system works well for music that has a relatively pronounced beat, yet without creating burdensome demands on computational resources. The algorithm is based on detecting rapid changes in energy within a short-term frequency representation. This produces a more reliable approach because overall energy can mask those spectral components that govern the perception of a beat. A least-square optimization then identifies the best tempo and downbeat location.  
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On the Acoustic Radiation from a Loudspeaker's Cabinet (PDF-310K)  
Kevin J. Bastyr and Dean E. Capone    234
Although it is well known that the walls of a loudspeaker cabinet vibrate at low frequencies, the authors determined the actual sound energy being radiated. Initially, a vibrometer was used to measure the surface velocity along the surface, and then a boundary-element method was used to model the acoustic radiation. By applying this method to production loudspeakers, changes in the internal bracing allow the designers to control these unwanted surface resonances, which are true radiating sources. The effects of enclosure vibration affect the overall radiation pattern of the loudspeaker and must be included in the design.  
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ENGINEERING REPORTS
The Virtual Loudspeaker Cabinet (PDF-97KB)  
J. R. Wright    244
The effective volume of a loudspeaker cabinet can be enlarged by as much as a factor of 3 if activated carbon is included inside the enclosure. The acoustic compliance, the ratio of change in volume with increased pressure, increases because the carbon absorbs and desorbs air. While it is still not commercially viable, the author demonstrates a successful laboratory model, which was judged to sound like a larger cabinet. Special care is needed to ensure that the carbon is uniformly distributed and that it does not absorb water.  
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LETTERS TO THE EDITOR
Comments on "Dipole Loudspeaker Response in Listening Rooms" and "Perception of Reverberation Time in Small Listening Rooms" (PDF-154K)  
Tomas Salava    248
Author's Reply  
James M. Kates    250
W. J. Davies    251
Comments on "President's Message"  
David Lloyd ben Yaacov Yehuda Klepper    251
Author's Reply  
Kees A. S. Immink    251
 
STANDARDS AND INFORMATION DOCUMENTS
AES Standards Committee News (PDF-98K)    253
Plane-wave tubes; MAD; acoustics and sound-source modeling; microphone measurement and characterization; listening tests  
 
FEATURES
24th Conference Preview, Banff (PDF-1.9MB)    258
    Calendar (PDF-628K)    260
    Program (PDF-485K)    262
    Registration Form (PDF-21K)    271
MIDI and Musical Instrument Control (PDF-1.1MB)    272
Game Audio: Follow-up to Workshop at 113th Convention (PDF-33K)    277
 
DEPARTMENTS
Review of Acoustical Patents (PDF-150K)    256
News of the Sections (PDF-499K)    279
Upcoming Meetings (PDF-71K)    285
Sound Track (PDF-10K)    286
New Products and Developments (PDF-58K)    287
Advertiser Internet Directory (PDF-38K)    288
Membership Information (PDF-9K)    289
In Memoriam (PDF-779K)    290
AES Special Publications (PDF-84K)    293
Sections Contacts Directory (PDF-33K)    298
AES Conventions and Conferences (PDF-47K)    304
 
EXTRAS
Cover & Sustaining Members List (PDF-25K)    
VIP List & Editorial Staff (PDF-40K)    
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