Breaking the sound barrier: Tunneling of acoustic waves through the forbidden transmission region of a one-dimensional acoustic band gap array

摘要

We demonstrate the tunneling of audio pulses through the forbidden transmission zone of an acoustic band gap array. The acoustic band gap is created in a waveguide with a periodically spaced series of dangling sidebranches. Using an impulse response method, the transmission properties of the array are characterized and the regions of forbidden transmission identified. Tunneling pulses, whose frequency content lies completely with the forbidden transmission region, are used to explore the concepts of tunneling time and group velocity. In an analog of experiments that are well known for electromagnetic waves, we show that the group velocity of the tunneling pulse is considerably larger than the speed of sound. The dynamics of pulse reshaping that lead to this phenomenon are discussed. (C) 2002 American Association of Physics Teachers. [References: 21]