... a stop watch and a convenient wall.
Step 1: The idea
Speed is how far something travels in a known time speed = distance / time.
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.