Detection of elastic modes in a solid-liquid-solid planar waveguide

Abstract

In this work, we demonstrate that acoustic ultra-short pulses can be used to characterize multiple guided modes in a solid-liquid-solid planar waveguide via the determination of the time of flight (τ) using the Short Time Fourier Transform (STFT). To obtain experimentally τ, we introduce a time dependent ultra-short acoustic signal s(t) at one side of a finite waveguide and we perform the STFT of the outgoing acoustic signal s′(t) from the other side. We have found that this technique is able to discriminate the signature of multiple even and odd modes at the same experimental run.

Recovery of transit times and frequencies of multiple pulses via the Short-Time Fourier Transform

“…Recently, we have revisited this problem investigating the transit times of high-order modes on SLS waveguides by using the Short-Time Fourier Transform (STFT) [5]. During this study, some of us that did not know the STFT technique were surprised by all the information that could be extracted of a pulse that at a first view looks only like a noisy signal [5]. In this work, we present a way to understand how the STFT allows determining the transit times of multiple pulses traveling simultaneously.…”