Tuning forks

  A struck bell, a plucked guitar string, and a dropped table knife will vibrate and make sounds. Each object vibrates at a particular frequency, known as its natural frequency. The frequency of a sound wave results in a particular pitch. The natural frequency of a small bell is higher than that of a large bell. When struck, the smaller bell will ring at a higher pitch.

  Tuning forks are used to tune musical instruments. The musician plays a note on his instrument and compares its pitch to the pitch made by the tuning fork. He adjusts his instrument so the pitch of each note match¬es the pitch made by the tuning fork for that note.

  When the bass player plays at the natural frequency of the tuning fork, the vibrations create resonance in the tuning fork. The vibration of an object at its natural frequency is called resonance. You can experiment with an instru¬ment to find the natural frequency of an unlabeled tuning fork by playing different notes and seeing which one causes the tuning fork to resonate.

  Finding the natural frequency of a tuning fork is just one example of resonance. Many objects have a natural frequency that is easily matched by other vibrating objects. The windows in our home rattle when the sound given off by a passing truck matches their natural frequency.