Download Entire Journal (8.1MB)
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| Volume 51 Number 4 | 2003 April |
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CONTENT Download Entire Journal (8.1MB) |
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| 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. | |
| Comment on this paper | |
| 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. | |
| Comment on this paper | |
| 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. | |
| Comment on this paper | |
| 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. | |
| Comment on this report | |
| 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) | |
| Ads In This Issue (HTML) | |