### Theory:

Apparatus required:
• A source of sound pulses
• A measuring tape
• A stopwatch
Procedure:
1. Using the measuring tape, determine the distance '$$d$$' between the source of sound pulse and the reflecting surface.
2. The receiver is positioned near the source. The source produces a sound pulse.
3. A stopwatch is used to record the time interval between the time the sound pulse is sent and the time the receiver receives the echo. The time interval is denoted by the letter '$$t$$'.
4. Carry out the experiment three to four times more. For a given number of pulses, the average time is calculated.
Calculation of sound speed:

The sound pulse emitted by the source travels a total distance of $$2d$$ between the source and the wall before returning to the receiver. The time it takes has been calculated to be $$t$$. As a result, the speed of a sound wave is determined by

$\begin{array}{l}\mathit{Speed}\phantom{\rule{0.147em}{0ex}}\mathit{of}\phantom{\rule{0.147em}{0ex}}\mathit{sound}=\frac{\mathit{distance}\phantom{\rule{0.147em}{0ex}}\mathit{travelled}}{\mathit{time}\phantom{\rule{0.147em}{0ex}}\mathit{taken}}\\ =\frac{2d}{t}\end{array}$ Reflection of sound waves