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with relatively inexpensive audio tweeters. In fact, since our SPL meter saturates at 130 dB, we can only estimate the total SPL. But it is worth noting that a phased array allows for the coherent superposition of the individual radiating elements and so we can achieve higher SPL than would otherwise be possible.
Summary
Using low-cost, off-the-shelf audio amplifiers and tweet- ers, we have designed and built an active acoustic phased array. The phasing, or time-shifting, of a single waveform is done by a bank of field programmable gate arrays which are connected to a personal computer via an Arduino microcon- troller. Although we have shown application to focusing or steering the array, it is possible to imagine much more sophisticated applications where the time delays are chosen to produce more complex space-time patterns. The modeling code which is available at
http://mesoscopic.mines.edu/mediawiki/index.php/Acoustic _Phased_Array
does a full field calculation; but it could easily be simpli- fied for far-field application, which would greatly speed it up. In addition to the simulation code (which is written in
Python), the design and materials used in the array are also available on the web site.
This material is based upon work supported in part by the U.S. Office of Naval Research as a Multi-disciplinary University Research Initiative on Sound and Electromagnetic Interacting Waves under grant number N00014-10-1-0958. AT
References
Azhari, H. (2010). Basics of Biomedical Ultrasound for Engineers (John Wiley & Sons, Inc., Hoboken, 2010). ISBN 978-0-470- 46547-9.
Chu, P. P. (2008). FPGA Prototyping by VHDL Examples: Xilinx Spartan-3 Version ( John Wiley & Sons, Inc., Hoboken, 2008) ISBN 978-0-470-18531-5.
Cobbold, R. S. C. (2007). Foundations of Biomedical Ultrasound (Oxford University Press, New York, 2007). ISBN13: 978-0-19- 516831-0.
Dowling, A. P. (1998). “Steady-state Radiation from Sources,” in Handbook of Acoustics edited by Malcolm J. Crocker (John Wiley & Sons, Inc., New York, 1998).
Pedroni, V. A. (2004). Circuit Design with VHDL (MIT Press, Cambridge, 2004). ISBN 0-262-16224-5.
Acoustical Society of America Books, Paper Colletions, Demos,Videos
Highlighting the collection is the Scientific Papers of Lord Rayleigh written from 1869-1919 on topics such as sound, mathematics, general mechanics, hydro-dynamics, and properties of gasses and Collected Works of Distinguished Acousticians - Isadore Rudnick with over 100 papers covering Rudnick’s research in physical acoustics. The ASA collection includes Auditory Demonstrations containing demos of various characteristics of hearing and Measuring Speech Production demonstrations for use in teaching courses on speech acoustics, physiology, and instrumentation.
Historical works include: Study of Speech and Hearing at Bell Telephone Laboratories containing
historical documents from AT&T archives. Technical Memoranda issued by the Acoustics Research Laboratory-Harvard University between 1946 and 1971 on topics such as bubbles, cavitation, and properties of solids, liquids, and gasses. Proceedings of the 1994 Sabine Centennial Symposium including papers covering virtually every topic in architectural acoustics and the Proceedings of the ASA’s 75th Anniversary.
The VHS videos in the collection are Speech Perception presented by Patricia K. Kuhl and Fifty Years of Speech Communication with lectures by distinguished researchers covering the development of the field of Speech Communication.
To view Tables of Contents and Prefaces and to purchase these publications please visit www.abdi-ecommerce10.com/asa/.
28 Acoustics Today, January 2013