The time-domain signature of negative acoustic group velocity in microsphere suspensions.
In the wake of recent reports of superluminal acoustic group velocities in sonic and ultrasonic regions of the acoustic spectrum, this paper describes the time-domain manifestation of such group velocities through simulations of the linear propagation of ultrasonic wave packets in a suspension of elastic microspheres. Conditions under which arbitrarily large and negative group velocities can be observed as the speed of a peak in the envelope of an acoustic pulse are described. Propagation simulations demonstrate the physical signature of negative group velocities, as well as the causal compliance of the superluminal acoustic pulses examined in this work.
Mobley
Joel
J
Department of Physics and Astronomy, National Center for Physical Acoustics, University of Mississippi, University, Mississippi 38677, USA.
D003198:Computer Simulation; D004548:Elasticity; D016014:Linear Models; D008863:Microspheres; D008962:Models, Theoretical; D009038:Motion; D016011:Normal Distribution; D011108:Polymers / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry*; D013016:Sound; D013997:Time Factors; D014465:Ultrasonics
D011108:Polymers; D012965:Sodium Chloride