EES 0836 Lecture Notes - Lecture 41: Rubber Band, Threshold Of Pain, Longitudinal Wave
3 Apr 2016
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Lecture - 41: sound, the nature of sound, ears and speakers, what is sound, sound is really tiny fluctuations of air pressure. Units of pressure: n/m2 or psi (lbs/square-inch: carried through air at 345 m/s (770 m. p. h) as compressions and rarefactions in air pressure, properties of waves, wavelength ( ) is measured from crest-to-crest. Or trough-to-trough, or upswing to upswing, etc: for traveling waves (sound, light, water), there is a speed (c, frequency (f) refers to how many cycles pass by per second. Measured in hertz, or hz: cycles per second. Associated with this is period: t = 1/f: these three are closely related: Can"t pull a (momentarily) neighboring molecule sideways. Only if a rubber band connected the molecules would this work. Fancy way of saying this: gases can"t support shear loads: air molecules can really only bump into one another, imagine people in a crowded train station with hands in pockets.
