Characteristics Of Sound by cmlang


									by: Ryan Fyfe

Sound in brief but remarkeable terms is a vibration, that our ears percieve by the sense of
hearing. Most commonly vibrations travel to our ears via the air. The ear then converts these
sound waves into nerve impulses that are sent to our brains, where the impulses become sound.
To say all that in a more technical language: Sound "is an alternation in pressure, particle
displacement, or particle velocity propagated in an elastic material" (Olson 1957). Sound is also
a series of mechanical compressions and rarefactions or longitudinal waves that successively
propagate through media that are at least a little compressible. What causes sound waves is
known as "the source of waves". Examples of sounds sources is: A violin string that vibrates
upon being bowed or plucked.

The four characteristics of sound are frequency, wavelength, amplitude and velocity.

The frequency of sound is the number of air pressure oscillations per second at a fixed point
occupied by a sound wave.

The amplitude is the magnitude of sound pressure change within the wave. Basically this is the
maximum amount of pressure at any point in the sound wave. A sound wave is caused literally
by increases in pressure at certain points causing a "domino effect" outward, the higher pressure
points are the crests in a - sound wave, and behind them are low
pressure points which tail them. These are known as the troughs on a wavelength graph. Sound's
propagation Velocity depends largely on the type, temperature and pressure of the medium
through which it propagates. Because air is nearly a perfect gas, the speed of sound does not
depend on air pressure.

The frequency range of sound that is audible to humans is approx. between 20 and 20,000 Hz.
This range of course varies between individuals, and goes down as are age increases. Sounds will
begin to damage our ears at 85 dBSPL and sounds above approximately 130 dBSPL will cause
pain, as a result are known as the: "threshold of pain". Of course again this range will vary
among individuals and will change with age.

This article was posted on November 07, 2005

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