You could try to "hack" an HC-SR04 to read the amplitude of the signal. Reading the following should give you some ideas, but it's definitely not a hand-holding "tutorial" that will lead you down a rosy path: HC-SR04 | David Pilling
And even if you can read the amplitude of the signal, like MorganS, I'm skeptical that doing so will help you achieve your goal in anything other than a laboratory setting....if that.