The didjeridu, or yidaki, is a simple tube about 1.5 m long, played with the lips, as in a tuba, but mostly producing just a tonal, rhythmic drone sound. The acoustic impedance spectra of performers' vocal tracts were measured while they played and compared with the radiated sound spectra. When the tongue is close to the hard palate, the vocal tract impedance has several maxima in the range 1-3...

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We give a mathematical analysis of the “time-reversal mirror”, in what concerns phenomena described by the genuine acoustic equation with Dirichlet or impedance boundary conditions. An ideal situation is first considered, followed by the boundary-data, impedance and internal time-reversal methods. We explore the relationship between local decay of energy and accuracy of the method, and explain ...

The thermal boundary resistance (TBR) is still a challengeable subject since its mechanism to explain quantitatively is not clear in spite of its importance. We performed non-equilibrium molecular dynamic (NEMD) simulation to evaluate TBR at an epitaxial solid interface composed of two different materials. Solid argon is selected as a simulation material since it is a non-conductor electrically...

We demonstrated a nearly impedance-matched high-overtone bulk acoustic resonator (HBAR) operating at super high frequency ranges using an epitaxial AlN piezoelectric layer directly grown on conductive SiC cavity substrate with no metal insertion. The small impedance mismatch was verified from the variation in free spectral range (FSR); experimentally obtained FSR spectra were greatly reproduced...