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Revision as of 18:47, 1 July 2007
Speed of Sound
The Speed of sound is measured in meters per second.The speed of sound is affected by several factors: temperature, humidity, and elasticity.
SOS ~ 344 m/s or 1130 f/s
NOTE: for class we will assume the speed of sound in air @ 20 degrees Celsius an 75% humidity is 344m/s
Speed of sound Calculator http://www.measure.demon.co.uk/Acoustics_Software/speed.html
Frequency/Period
Sound is a periodic event. This means that there is a fixed amount of time between different events.The Frequency component of a sound wave affects the pitch of the sound.
Frequency if the measure of how many cycles a wave complete per second.
Frequency (f) is measures in Hertz
Period (T) in the inverse of infrequency is is measured in seconds
Frequency = Cycles/Second Period = Seconds/Cycle
f = 1/T T = 1/f
Different types of frequency components periodic / aperiodic.
Periodic
- sound that has a measurable frequency
Aperiodic
- sound that is mostly random
It is assumed the humans can hear frequencies from 20Hz to 20,000 Hz.
20-20KHz Sweep
- http://iam.colum.edu/sound/media/sweep20-20.wav 41kb,16 bit 3.7megs
Resonance
Wavelength
Wavelength is measured in distance (ft. of m)
The actual physical length of a single cycle of a wave
Wavelength = speed of sound / Frequency in Hz
- λ = SOS/f
wavelength = speed of sound * period
- λ = SOS*T
The wavelength of a sound wave varies greatly with the frequency of the wave. A 20 kHz wave has a wavelength of 1.72 (0.7 in)cm while a 20 Hz wave has a wavelength of 17.2 m (~56 ft.).
Examples http://iam.colum.edu/MTD2/lectures/week1_examples.htm