Every person, as a kid, always enjoyed echoes. If you say you didn't, then your lying. This past unit, I learned about sound and it's reflection off of objects. The reflection of sound off of an object is known as an echo. As a result of finding this, I know how to find the distance between me and an object based on the knowledge that d=v(t) and sound travels at 331 m/s in air at stp. By measuring the amount of time it takes for the sound to come back, and dividing it by two, I can find the distance between me and an object. Boom. I bet you all will do this tomorrow.