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Unformatted text preview: What is Sound?
A mechanical disturbance propagated through an elastic medium. Basic Quantities
Mechanical Disturbance Displacement, x Time, t l Kinematics
l l Basic Quantities
l l l Graphical Representation
l l l l Mass, m Elastic Force Dynamics Oscillation Modes of Vibration Superposition Complex Sound Scope Peak Amplitude
Maximum displacement, A.
+ Amplitude 0 Time, t large A small A Some Typical dB Levels
dB SPL 0 40 60 80 90-100 130-150 Condition of Measurement Absolute threshold 3-kHz, free field Very quiet living room Average conversation level Shouting Passing train 100 ft. from jet engine Frequency
Number of cycles per second, f in Hz. Range of Audible Frequencies
20-100 Hz Bass Guitar, Bass Drums Piano, Flute Speech Cymbals, Snare + Amplitude 0 Time, t 100-1000 Hz 1.0-8.0 kHz 8.0-20.0 kHz Starting Phase
Starting angle, 0 in degrees
+ Amplitude 0 Time, t Sound in Field with Obstacles
l Large l l l l Bends around Wavelength, Large , low f Head shadow Comparison to light Small Head Shadow Sound in Field with Obstacles
l l Sound in Enclosures
l l l l Bounces off of Incident & reflected wave Phantom source Small , high f Phantom Source l l Nodes & Antinodes Coloration Hearing in rooms A = x+y , solve for x & y ...
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This note was uploaded on 03/21/2012 for the course COM DIS 110 taught by Professor Weismer during the Fall '08 term at Wisconsin.
- Fall '08