Speed of Sound and Echoes

The speed of sound is the distance travelled by a sound wave per unit time. Sound speed depends on the medium. It is generally: fastest in solids, slower in liquids, slowest in gases. In air near room temperature, a commonly used approximate value is: v ≈ 340 m/s

Sound moves through interactions between neighbouring particles. Materials in which disturbances are transferred efficiently can transmit sound more rapidly.

An **echo** is a reflected sound heard separately from the original sound. The sound travels to a reflecting surface and then returns to the listener.

Because the sound travels to the obstacle and back: **distance to obstacle = vt/2** where: v = sound speed; t = total round-trip time.

Echo time = 2.0 s. v = 340 m/s. Distance: **d = vt/2** = 340 × 22 = **340 m**