Bath, Pennsylvania - U.S.A.

Charles A. Giannetta

Meteorologist

Professor

Meteorology Charles A. Giannetta Meteorologist - Professor "Sound In The Atmosphere" Sound is a disturbance which occurs in the air caused by vibrations or shock. Particles of air vibrate abn creats pressure waves which are capable of being hard by the human ear. All sound must be transimmited through some elastic nedium: (Solid, Liquid, Gas) before it can be heard. If there were not particles of matter to vibrate and pass along the pressure wav, sound would not exist. Sound travels about 1,00 feet per second at the Earth's surface. It travels at the same rate in all directions from the source. Example: A train whistle" Car Horn: A person speaking: The velocity is effected by factors such as temperature, humidity & also altitude. In warm air at the surface, the air molecules are less densely packed and will transmit sound faster than if the air were cooler. Sound velocity increases slightly for each deegree the temperature increases. At the surface of the Earth wuth a temperature of 32 degrres F., sound has been determined to be 1,000 feet per socond.

Meteorology Charles A. Giannetta Meteorologist - Professor "Sound In The Atmosphere Continued" An increase in humidity also results in an increase in the speed of sound. The density of humid air is lessened and therefore sound travels faster through it. Air thins out at very high altidudes to a point where there are not enough particles to transmit sound. Audible sounds are estimated not to be heard at altitudes of 80 miles or higher above the Earth. Many factors limit the distances at which sound can be heard. One of these is the wind. The wind blows strong and steady or is gusty and it often distorts the shape of the sound wave and moves it away fom the source sound wave. The wind moves the sound away from the hearing range in short distances from the sound source. Air also moves vertically and horziontal and breaks the sound wave. These vertical and horizontal motions of air cause the sound wave to lose unity, strength and direction and so the sound wave fades. When the sound waves enter air of different density, part of the energy of the sound is lost or reflected.

© 2013 Charles A. Giannetta

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