WHAT IS PITCH: Sound waves are pressure waves. A vibrating object creates a disturbance in the surrounding air, much like a stone cast in a quiet pond will cause waves to ripple outward from the spot where the stone hit. All sound waves have wavelength and frequency. Objects that vibrate very quickly create short wavelengths and a high-pitched sound. Objects that vibrate very slowly create long wavelengths and a low-pitched sound. Frequency measures the speed of vibration in a unit called a Hertz (Hz), and 1 Hz is equivalent to 1 vibration per second. Pluck a string on a guitar, and it might vibrate 500 times per second, so the sound wave's frequency would be 500 Hertz. Pitch simply denotes those frequencies within the range of human hearing (from about 20 Hz to 20,000 Hz). The faster the rate of vibration, the higher the pitch; the slower the rate of vibration, the lower the pitch.
WHAT MAKES ELECTRIC GUITARS LOUD? Essentially this is possible because of two items: an amplifier and a pick-up. Amplifiers, as you may expect, increase the amplitude or volume of sound and other signals. For audio amplifiers that means a sound must be turned into an electric signal, and sent into the amplifier before it emerges many times louder than the level at which it was originally produced. It is essentially a speaker whose source can be a guitar, a CD, a microphone, or many other items. A pick-up transforms the movement of guitar strings into an electrical signal that can be transmitted to amplifiers or recording equipment. Some use magnets wrapped inside a coil of wire, while others use alternate methods, such as piezoelectric crystals (which respond to physical stress or deformity by creating electrical energy).
The Institute of Electrical and Electronics Engineers, Inc. and the American Association of Physics Teachers contributed to the information contained in the TV portion of this report.
