Step 1: The idea
In everyday life, speed is generally measured in either miles per hour (or kilometres per hour; most of the world is metric). Higher speeds, especially in a scientific or engineering context, are usually measured in metres per second (m/s, ms-1), and that is what we will use in this Instructable.
We will measure the time it takes for sound to travel a known distance by using rhythmic echoes.
Step 2: The equipment
To generate an echo, we need a hard flat surface in a fairly uncluttered space. A wall in a school playground is perfect.
We need to time the echo's journey, so we need a stopwatch. Actually, we are going to use several stopwatches to eliminate human error: a small group of Science Clubbers will each use a stopwatch, and an average will be taken of their results,
To find the distance? part of the equation, we need to know how far we are from the wall. This should be measured in metres, either with the school-child's favourite, the click wheel, or with a dirty great tape measure.