“…3c and 3d, respectively. It is well known that if the humidity and temperature are neglected, the formula for calculating the length of a closed pipe is L = (v/f)/4 (the theoretical length, L, equals the speed of sound, v, divided by the frequency of the sound in hertz, f, with the resulting quantity being divided by 4, 15 as shown in Fig. 4 (dashed line)).…”