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Properties of Sound

Audiology PowerPoint 2, study HLS and equations separately

Sound Vibrations transmitted through an elastic medium (NOT a vacuum)
Condensation Air molecules are pushed closer together, creating a movement that affects the air further on. (Up on a wavelength, high pressure)
Rarefaction Partial vacuum forms, air molecules nearby move in leaving a rarefied zone behind. (Down on a wavelength, low pressure)
Wave of sound a succession of compressions and rarefactions
Oscilogram records pressure variations of sound waves
Wavelength the distance required to complete one cycle. Measured in meters(m) or seconds (s)
Period (T) duration required to complete a cycle. Measured in seconds (s)
How does Period relate to Pitch? The longer the cycle, the lower the pitch.
Frequency (F) the number of cycles completed per second. Measured in Hertz (Hz). (wave/sec =Hertz)
How does Period relate to Frequency? they are inversely proportional. As the period increases, the frequency of vibration decreases.
How does Frequency relate to Pitch? the lower the frequency, the lower the pitch.
Period (s) = 1/Frequency
The Velocity (m/s) = wavelength (m) x frequency (Hz)
Pure tone a sound wave made of a single frequency
Pure tones in phase when their waveform have the same starting point, create constructive interference
Pure tones in opposition of phase when their waveform have opposite starting point, create destructive interference, noise cancellation
Pure tones out of phase when their waveform have different starting points
Beats perceived fluctuations in amplitude when 2 tones of similar frequency are presented together
Noise a complex sound without period
Amplitude the maximum displacement from zero in a sound wave Relates to loudness. Reflects the amount of pressure produced during condensation.
Smallest audible sound pressure is ~20 MPa
Sound waves begin to damage hearing at ~200,000,000 MPA or ~200 PA
dB scale Bel (B) and decibel (dB) logarithmic units of measurement. A way to shrink a large number scale to be manageable, convenient.
Log 1 = 0
Log 1,000 = 3
dB (SPL) = 20 log P - 20 log Pr = 20 log (P/Pr)
Pressure of reference the threshold of audibility, Pr = 20 MPa
Range of Auditory Perception: Frequency sounds lower than 20 Hz and higher than 20 kHz (20,000 Hz) can not be heard
Range of Auditory Perception: Loudness lower limit of audibility is 0 dB, physical pain at 130-140 dB
Created by: 100000299709410