Halliday, Resnick & Walker — Waves–II: Problem 84

The speed of sound in a certain metal is \(v_m\). One end of a long pipe of that metal of length \(L\) is struck a hard blow. A listener at the other end hears two sounds, one from the wave that travels along the pipe's metal wall and the other from the wave that travels through the air inside the pipe. (a) If \(v\) is the speed of sound in air, what is the time interval \(\Delta t\) between the arrivals of the two sounds at the listener's ear? (b) If \(\Delta t = 1.00 \text{ s}\) and the metal is steel, what is the length \(L\)?