Speed

Just your ear and a good internal stopwatch. Sound travels at roughly 1,100 feet per second through the air, as far as I know. One good way to do this is to find an outdoor field where a baseball team is working out and taking batting practice. Step off about 370 yards from the home-plate area, turn around, face the batter, and you will notice that it takes about one second from the time you see the bat making contact to the moment you actually hear the sound. Another example is observing and listening to lightning and thunder during thunderstorms. When you see a lightning strike, then count "one thousand one, one thousand two, one thousand three," etc., or roughly one-second intervals, then listen for the ensuing thunder. Every second represents about one-fifth of a mile. So if you count five seconds from the time you see a flash of lightning in the distance to the time you hear the thunder rolling in, then the center of gthat storm is roughly a mile away. In short, it is easy to measure the speed of sound without any fancy equipment.