The Cheat Sheet: Sound Characteristics

flip-michaels-1991cheat-sheet-logo

by Flip Michaels

SOUND CHARACTERISTICS. Do you remember them?

Be quick or be dead.

Okay. There are three:

SOUND FREQUENCY, SOUND INTENSITY, SOUND DIRECTION.

The surround sound invasion allows me to assume that one cannot escape the daily review of SOUND DIRECTION. So, let's discuss SOUND FREQUENCY and SOUND INTENSITY.

The facts!

Sound is produced by a vibrating body. As a body vibrates back and forth, it creates pressure variations in the surrounding air, which is pushed outward in waves. These sound waves are cyclical and can be illustrated by the "sine wave."

1-Hz-and-2-Hz-sine-waves

These waves vary in both frequency (the number of cycles per second) and intensity (the strength, or "amplitude" of the wave).

The faster the body vibrates in the air, the greater the number of cycles produced and the higher the sound's frequency. Our industry, as you know, notes sound frequency as "pitch."

A high-pitched sound produces a great many sound waves per second. Whereas, a low-pitched sound produces far fewer vibrations per second. We measure a sound's frequency in "hertz (Hz)," meaning the number of cycles per second produced by a sound source.

Check it out.

People are capable of hearing frequencies between 16 and 16,000 Hz depending on gender, age, and health.

We're most sensitive to sounds between 500-4000 Hz (the range of sound frequency most prevalent in human speech).

Professional audio equipment can reproduce sound frequencies from about 15 Hz - 20,000 Hz.

Moving on.

The intensity of sound depends on the amount of energy used to produce the pressure variations in the air. The more energy used, the greater are the pressure variations and the more intense the sound. We perceive the intensity of sound as loudness.

Our sense of loudness is more a relative measure than an absolute scale, so we generally are working with a ratio of the intensity, or loudness, of one sound to that of another. We measure this intensity ratio in "decibels (dB)."

Decibels are measured on a logarithmic scale which allows us to express very large physical values with a rather small and convenient scale of numbers. The decibel scale is designed so that a doubling of intensity is expressed as a change of 3 dB. Therefore, a change from 3 to 6 dB is a doubling of sound, as is a change from 6 to 9 dB, or from 15 to 18 dB.

WHISPER -- approximately 30 dB

PAIN THRESHOLD -- approximately 140 dB

(This represents a range of 70 billion to 1 !)

Hey... after this column, my decibels hertz! Remember that it's not only important to know the measurements, but the facts behind them too. As the years pass, take that extra effort to hold on to the basics. Happy New Year! And, hey! I'm as serious as a train wreck!