Sound is energy which is generated by a source, transmitted through a medium, and received by a receiver. For example, a piano string vibrates when the key is struck, generating a sound. The vibration alternately compresses and expands the surrounding air, transmitting the sound in waves of pressure changes. When the waves reach your ear, you receive that sound.
If you remove any of the above conditions, there is no sound. There is no sound in space, for example, since no medium exists to transmit sound waves. Sound has three (3) measurable components:
FREQUENCY is the rate of vibration, determining how high or low the pitch is. Frequency is measured in cycles per second, or Hetz (Hz). The wave length associated with a given frequency is the distance the sound travels in one cycle. It is related to the frequency like this:
Healthy children can hear from 20 to 20,000 Hz, but the human ear is most sensitive in the range of 100 to 5000 Hz. Most of our music, speech and other critical sounds are found within this range.
AMPLITUDE is the magnitude of the vibration, which determines how loud the sound is. So in essence, more vibration equals higher amplitude (volume). Amplitude is measured in decibels (dB), which can range from the threshold of hearing 0 dB to the threshold of pain which is 140 dB.
DURATION is the length of time that a particular sound lasts, measured in seconds. The duration may indicate how long the source of the sound is vibrating or how much the sound is reverberating (echoing). Some sound levels will cause immediate damage to an unprotected ear. Oftern damage will be caused only if the duration of the sound is too long.
In Part II we’ll discuss Sound Control.