I am using the following system: Ultrasonic chirp signals with central frequency 100kHz are being transmitted using ultrasonic sensor. After the transmission through the medium(air/solid/liquid/combination) they are being received with hydrophone. The system is being controled by DSP and signal generation and acquisition is obtained via DAC and ADC. Our aim is to detect the time of arrival between transmission and reception. My mentor suggested that I could use something with FFT to observe reflections, but I am struggling to find information on the internet about it. Does anyone have a suggestion how that could be done using FFT, or any other method?