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Acoustic energy output and coupling effect of a pair of thermoacoustic lasers



Two identical TA (ThermoAcoustic) lasers were constructed, tested, and characterized for the generation and manipulation of high-amplitude acoustic waves from heat. Pyrex glass tubes with one open end and ceramics used in automobile catalytic converters were employed to fabricate the TA lasers. The ceramic stack in each TA laser was heated by a thin NiCr (nichrome) resistance wire at one end, and cooled at the other end by radiation and natural convection of atmospheric air. Generated acoustic energy and sound waves were analyzed for different power input rates and laser position arrangements. Changes in wave amplitude and phase difference due to triggered excitation and cross talking between the two TA lasers were investigated. Also tested and characterized were the focusing and synchronization of the two laser outputs for manipulating the acoustic waves and energy intensity. Direct applications of large quantities of acoustic energy generated by multiple TA lasers were addressed. It was found that the sound waves generated by a pair of identical TA lasers were almost 180° out of phase when the openings of the two lasers were very close to each other, resulting in much lower sound energy levels at the focusing point. When the two lasers were placed far apart, the phase difference between the two laser outputs varied with time. Amplitudes of both sound waves increased slightly when the two laser outputs were in phase. Copyright © 2011 John Wiley & Sons, Ltd.