Acoustic Refractive Index Measurement Using Tone Burst Signal as an Alternative to Broadband Pulse by Through-Transmission Method

This study relates to a precise measurement technique of the acoustic refractive index (ARI) of dispersive materials. The water immersion measuring device was configured so that the sample and the transducer were easily exchanged. To minimize the peak-frequency shift of the signal passing through the sample, a narrowband tone burst signal was used. Considerations for the number of cycles, thickness, and refractive index to avoid overlapping reflected waves inside the sample were also described. By reflecting the phase by time of flight and the phase obtained through FFT, it was possible to obtain a result showing a more consistent trend of frequency-dependent ARI. A method of reflecting the diffraction loss and transmission loss, which are easily overlooked in the transmission method, in the attenuation coefficient measurement is also considered. The material used in this study is commercial polydimethylsiloxane (PDMS), which is widely used as an acoustic lens for medical ultrasound probes