MCELLBI C61 Chapter Notes - Chapter 15: Sound, Rarefaction, Density Of Air
17 May 2020
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If sound is de ned as an experience, it"d require something capable of mental experience. That requires having an ear + a nervous system to process the signals generated by it. If sound is de ned as variation in air pressure generated by an event, then that air pressure variation presumably exists whether or not any beings with ears and nervous systems are near. Dictionary de nitions of sound account for both mental experience + physical vibration. The result is a rhythmic pattern of air pressure variation that moves out into space as waves of alternating compression and rarefaction. Depicted in graphical form as a sinusoid of air pressure + time. A sound wave moves through air at a speed of about 1,100 ft/s, or 335 m/s, or 750 mph. For any moving wave: velocity (ft/s) = frequency (hz, cycles/s) wavelength (ft/cycle) Thus, for an air pressure variation oscillating at 200 hz, the distance of one.
