![]() ![]() As the source continues to vibrate the medium, the vibrations propagate away from the source at the speed of sound and are forming the sound wave. The sound source creates vibrations in the surrounding medium. The sound waves are generated by a sound source (vibrating diaphragm or a stereo speaker). Sound cannot propagate without a medium - it propagates through compressible media such as air, water and solids as longitudinal waves and also as transverse waves in solids. So, a sound pressure change of 1 Pa RMS (equals 94 dB) would only change the overall pressure between 101323.26.4 Pa. ![]() The atmospheric (constant) pressure depending on height above sea level is 1013,25 hPa = 101325 Pa = 1013,25 mbar = 1,01325 bar. ![]() To understand the proportions, we have to know that we are surrounded by constant atmospheric pressure while our ear only picks up very small pressure changes on top of that. Because of the inertia of the particle, it overshoots the resting position, bringing into play elastic forces in the opposite direction, and so on. If an air particle is displaced from its original position, elastic forces of the air tend to restore it to its original position. Sound needs a medium to distribute and the speed of sound depends on the media: Frequencies below we call sub-sonic, frequencies above ultra-sonic. The human ear covers a range of around 20 to 20 000 Hz, depending on age. The sound is a mechanical wave which is an oscillation of pressure transmitted through a medium (like air or water), composed of frequencies within the hearing range. ![]()
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