Question

The ability to hear a "pin drop" is the sign of sensitive hearing. Suppose a 0.46-g pin is dropped from a height of 23 cm, and that the pin emits sound for 2.5 ms when it lands. Assuming all of the mechanical energy of the pin is converted to sound energy, and that the sound radiates uniformly in all directions, find the maximum distance from which a person can hear the pin drop. (This is the theoretical maximum distance, but atmospheric absorption and other factors will make the actual maximum distance considerably smaller.)

Answer 1

The potential energy of the pin is, - (0.46x103 kg (9.8) (0.23 m) 1.03684x10-3 J The power emitted by thepin is, E 1.03684×1 -0.414736 w 2.5x10-3s The sound intensity at the threshold of hearing is, I0 - 10-12 W/m' The intensity of the sound is, CZE ATI。 (0.414736 w) (0.414736 W 47 10-12 W/m2 -1.82x103 m