Sound in brief, is important, but is a vibration, that our ears perceive by the sense of hearing. common vibrations travel to our ears through the air. The ear converts sound waves into nerve impulses that are sent to our brain where the impulses become sound. To say all this in more technical language: Sound "is an alternation in pressure, particle displacement, or particle velocity propagated in an elastic material" (Olson 1957). The sound is also a series of mechanicalcompressions and rarefactions or longitudinal waves that successively propagate through media that are compressed at least a little. "What causes the sound waves is known as the source of the waves." Examples of sounds sources is: a violin string that vibrates after being bent or pinched.
The four characteristics of sound are frequency, wavelength, amplitude and speed.
The frequency of sound is the number of oscillations of air pressure per second at a fixed point occupied by asound wave.
The width is the amount of variation in sound pressure wave. Basically this is the maximum amount of pressure at any point of the sound wave. Literally a sound wave is caused by increased pressure at certain points causing a "domino effect" outward, the higher pressure points are the crests of a sound wave, and behind them are low pressure points including the tail . These are known as depressions in a graph of wavelength. Speed of sound propagationdepends largely on the type, temperature and pressure of the medium through which it travels. Because the air is almost 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 among individuals, and lower as age increased. Sounds begin to damage the ears at 85 dB SPL and sounds above approximately 130 dB SPL cause pain, therefore knownas "pain threshold." It is clear that in this interval varies among individuals and changes with age.
See Also : Whole House Generator About Sales Wirless baby monitor Store The Best Wireless Baby Monitors Making Ebooks Camera Telephoto Lens