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Period
Time in seconds (don’t forget to convert msec to sec)
Periodic
Tonal, have pitch, vowels, integer multiple harmonic
Aperiodic
Noisy, no tone, no pitch, static, consonants, no clear organization
Pure sound aka sine wave
Not real in nature, only made by a machine, ONE sound
Find wavelengths
Wave length = c / f
What is the speed of sound ( c ) ?
343 m/sec
Find the frequency
F = 1/t
How to find the period of a complex periodic sound
Find the period of the lowest frequency t=1/f
Wavelength
Distance in meters (don’t forget to convert mm to m)
Convert 2 msec into seconds
.002
How do sound waves travel via air
Molecule vibration in an elastic medium
Compression
Positive pressure, top of wave
Rarefaction
Negative pressure, bottom of wave
When sounds fades, due to friction, its called
Damping
Sound wave propagation
Sound waves travel in all directions from the sound source
Frequency
Cycles per second, expressed in Hz
What is audiology?
Came from noise exposure from modern weaponry
What does presbycusis mean?
Age related hearing loss
What is hearing loss associated with?
Falls, depression, isolation, loneliness, reduced quality of life
Acoustic energy
Air molecule vibration
Mechanical energy
Ear drum, biological microphone
Electrochemical energy
Nervous system
Vibration
Tuning fork, a to-and-from motion
Properties of sound source vibration
Equilibrium (resting position)
Maximum displacement in one direction
Maximum displacement in another direction
Elasticity: wants to go back to equilibrium
Start at resting position, vibrates and restoring force because of inertia over shoots in the maximum direction and repeats until returning to resting
What is a vibration
A disturbance in both space and time (a wave)
Inertia
The tendency of an object set into motion to remain in motion
Elasticity
A physical property where a deformed object returns to its original form (related to restoring force)
Restoring force
The force that opposes the deformation of an elastic material or medium
Elasticity does not equal flexibility
Steel strings are more elastic than rubber strings because they resist more to the external force
Can you hear in a vacuum such as space?
Since there are no air molecules present to vibrate, there is no sound. There is no medium
The Doppler effect
Think of what you hear when a car comes towards you, away from you, or passes you left to right
Where do decibels come from
It’s a logarithmic scale to pascals
What is 0 decibels
Average quietest noise people can hear “reference value”
Note 
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