title: Classroom demonstrations of acoustic beamforming.
abstract: A tabletop apparatus permitting demonstrations and hands-on student exercises in the acoustic beamforming of linear arrays is described. The apparatus can be used to demonstrate how interference effects from two or more linearly arranged sources produce patterns of maxima and minima as described by theory. A transmitting array is attached to the top of a rotating table and a receiving transducer provides voltages to a signal processor. Students measure the angular speed of the rotating table and the voltages produced by the receiving transducer as a function of time. These data can be analyzed in a spreadsheet program and compared to theory. The angles at which signal maxima occur correspond well to theory and useful teaching discussions result from comparisons of signal maxima magnitudes. The spreadsheet analysis can also provide the students a graphical demonstration of l'Hôpital's rule.
authors.affiliation: Physics Department, U.S. Naval Academy, 572C Holloway Road, Annapolis, Maryland 21402, USA. carman@usna.edu
authors.forename: Jessie C
authors.initials: JC
authors.lastname: Carman