Lecture 1 Slides

Lecture 1 Slides - What is Sound? A mechanical disturbance...

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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 Elastic Medium l l l Graphical Representation Time Waveform 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 Diffraction 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 Reflection Wall l l Sound in Enclosures Interference 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.

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