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PreAP Sound. Sound. Sound is a longitudinal or compression wave: Carries energy that is felt as a force. Eardrums. Feel the sound and convert it to something that is audible. Speed of Sound. Differs based on the medium Sound works by transferring between atoms
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Sound • Sound is a longitudinal or compression wave: • Carries energy that is felt as a force
Eardrums • Feel the sound and convert it to something that is audible
Speed of Sound • Differs based on the medium • Sound works by transferring between atoms • Speed of Sound in Air = 343 m/s • Speed of Sound in Water = 1483 m/s • Speed of Sound in Steel = 4512 m/s
Examples • Determine the time it takes for a sound to travel 10 meters in air • If a man has his ear pressed to a steel door that is 2 m thick and the time it takes for sound to travel is 0.0058 seconds. Determine the distance in air between the person and the wall
Examples How does the cup aide in the student hearing the sound?
Faster than Sound • Mach 1 is speed of sound • Mach 2 is speed of sound X 2
Sonar • Sound leaves and returns time it takes to return determines distance
Example • Determine the distance between a submarine and an enemy ship if it takes 2 seconds for the ping to occur
Frequency of Sound • Described in terms of pitch • Things with High frequency have high pitch and vice versa
Human Hearing Range • Humans can here between 20-20,000 Hz • If a sound is below 20 Hz it is infrasonic • If a sound is above 20,000 Hz it is ultrasonic
Doppler Effect • The apparent change in the frequency due to the motion of the source
Doppler Effect • Can be calculated using fo = fs(1/[1+/- (v / vs)]) • Measures the observed frequency for any moving object
Examples • Determine the what velocity will change the frequency from 12 Hz to 15 Hz • Determine the observed frequency if the initial frequency if 500 Hz and the object moves away from you at 10 m/s
Sound Intensity Measure of energy per area Intensity = P 4πr2
Example Pg 488 (ch 13) #2
Loudness • Loudness is measured in decibels • It is a logarithmic scale
Resonance Forced vibrations that match the natural frequency of vibration