Download presentation
Presentation is loading. Please wait.
1
Conceptual Physics Hewitt, 1999 Bloom High School
2
26.1 The Origin of Sound All sound produced by vibration of an object Strings in instrument, reed in a sax, etc. Pitch- how our anatomy interprets frequency (tone or note) Human range 20-20,000 Hertz Infrasonic- frequencies <20 Hertz Elephants, whales, earthquakes Ultrasonic- frequencies >20,000 Hertz Plastic welding, jewelry cleaning, mixing
3
26.2 Sound in Air Sound travels in longitudinal waves Compression- molecules pushed together represent a crest Rarefraction- molecules pulled apart represent a trough
4
Rubens Tubes Uses a flammable gas in a metal tube to show how frequency and wavelength are related to compressions and rarefractions http://www.youtube.com/watch?v=FOYXomUFyb8
5
26.3 Media that Transmit Sound Sound needs something to compress to transmit energy Gases- air, usually Liquids- water (whale and dolphin communications) Solids- earthquakes, railroad tracks Sound cannot travel in space Ever hear the Death Star explode?
6
26.4 Speed of Sound Speed of sound is dependant on how close the molecules are The closer they are, the faster the speed Solids- fastest Liquids- fast Gases- slowest Temperature dependant- the faster the molecules are moving, the faster the speed of sound v=330m/s + (T)(0.6m/°Cs) Speed of sound in air, T=temperature in °C v=d/t (still and always)
7
26.5 Loudness Loudness- how our anatomy interprets amplitude (volume) Decibel (dB)- 1/10 th of a bel Each level 10 times as loud as the prior level
8
26.6 Forced Vibrations Forced vibrations- a non-vibrating object that vibrates as a result of other vibrations Tuning fork alone vs. tuning fork on a tabletop
9
26.7 Natural Frequency Natural frequency- depends on material, elasticity of object, shape of object Small brass bell vs. large brass bell Baseball bat vs. wrench dropped on the floor Champagne glass
10
26.8 Resonance Resonance- when the frequency of a forced vibration matches a natural vibration Kicking your legs while swinging to go higher Increase in amplitude (loudness) Crest overlaps with crest Tacoma Narrows Bridge Collapse
11
26.9 Interference Interference- waves from two separate sources overlapping Constructive interference- the crest of one wave overlaps with the crest of another wave Increases amplitude (loudness) Destructive interference- the crest of one wave overlaps with the trough of another wave Decreases amplitude (loudness) http://www.falstad.com/interference/
12
26.10 Beats Beats- the periodic variation in loudness Caused by the interference of two slightly different frequencies www.sciencejoywagon.com/explrsci/media/tonebeat.htm Used to tune instruments C:\Program Files\Wolfram Research\Mathematica Player\7.0\MathematicaPlayer.exe C:\Program Files\Wolfram Research\Mathematica Player\7.0\MathematicaPlayer.exe
Similar presentations
© 2024 SlidePlayer.com Inc.
All rights reserved.