Question

Speed of sound in air is 330 ms⁻¹. A man standing at a distance of 165 m from a high wall, claps his hands.

1. Will the man hear a distinct echo?
2. Give a reason for your answer in (i).

Answer 1

(i) Yes, the man will hear a distinct echo.

(ii) The sound travels to the wall and back, so the total distance travelled is 2 × 165 = 330 m.

The time taken is t = distance ÷ speed = 330 ÷ 330 = 1 s.

Since this is greater than the persistence of hearing (0.1 s), the reflected sound is heard as a distinct echo.