http://www.acs.psu.edu/drussell/Demos/StandingWaves/StandingWaves.html

http://www.acs.psu.edu/drussell/demos/waves/wavemotion.html

Vibrations and Waves

Amplitude – maximum displacement from equilibrium

Frequency – number of cycles or vibrations per unit of time

Period – the time it takes to execute a complete cycle of motion

Fundamental frequency A guitar string = ½ a wavelength

Vibration is greatest at the antinode

So a wavelength is twice the string length... λ = 2L

Velocity = frequency x wavelength, or v = fλ or f = v/t

now substitute value for f ... f 1 = v/λ = v/2L

L

Frequency is inversely proportional to wavelength

Pendulum Lab: http://phet.colorado.edu/en/simulation/pendulum-lab

Longitudinal Sound wave

Sound wave - visual

Visual soundwavehttps://www.youtube.com/watch?v=s9GBf8y0lY0

Or Compression Wave

Wave in tub

Decibles:https://www.youtube.com/watch?v=jCQRBJwUt2s

HarmonicsHarmonics are the integral multiples of the

fundamental frequency

Harmonic series of standing waves on a vibrating string:frequency = harmonic number X speed of waves

(2)(length of string)or... f n = n x v / 2L

Harmonic seriesStanding waves in an air column:

If both ends are open, all harmonics are present. Antinodes exist at the end of the tube (the opposite of strings!)

Distance between nodes = ½ wavelength or...

d = ½ λ

This is the same as a vibrating string... fn = v/2L

Harmonic seriesStanding waves in an air column:

If one end is closed, only odd harmonics are present. The closed end is a node and the open end is an antinodes.

Fundamental frequency: f 1 = v/λ = v/4L

Third harmonic has ¾ of a wavelength so λ = 4/3 L

f 3 = v = 3v = 3v = 3f1 λ 4/3L 4L

fn = n x v/4L v = speed of sound in the tuben = harmonic

numberL = length of tube

Fundamental frequency is the lowest possible f of a standing wave

Decibels – unit measuring the intensity of sound

0 dB = smallest audible sound 10 dB = 101 threshold of good hearing20 dB = 102 leaves rustling, ticking of watch30 dB = 103 whisper40 dB = 104 quiet library50 dB = 105 moderate rainfall60 dB = 106 normal voice; dishwasher70 dB = 107 busy street traffic80 dB = 108 vacuum cleaner; alarm clock90 dB = 109 lawnmower; hair dryer, blender100 dB = 1010 mp3 player at full volume; lawn mower110 dB = 1011 front row at a rock concert; car horn120 dB = 1012 police siren130 dB = 1013 threshold of pain; jackhammer140 dB = 1014 military jet takeoff; gunshot; fireworks150 dB = 1015 instant perforation of the eardrum

The amount of energy transported through a medium is called the intensity of the wave.

Intensity = Power/area

Unit = watts/meter2

Exponential scale (logarithm)

Amplitude – measureableLoudness – human perception, duration, frequency

Stereo cilia (really microvilli, contain actin filaments)

Located on the basilar membrane in one of the three compartments of the Cochlea. (16,000-20,000 of the hair-like cells)

When broken, the signal is constantly sent to the brain (tinnitus)

Any sound above 85 dB can cause hearing loss.Related both to the power as well as length of exposure.

http://www.animations.physics.unsw.edu.au/jw/dB.htm#soundfiles

Sound

https://www.youtube.com/watch?v=Ude8pPjawKI

NPR – The Sound Book (“Sound Intriguing: The World’s Most Interesting Noises”)

http://www.npr.org/player/v2/mediaPlayer.html?action=1&t=1&islist=false&id=274717997&m=274786019

https://www.youtube.com/watch?v=hxIuIxqo2So

https://www.youtube.com/watch?v=uUpDG680uew

William Tell Overture

The coolest things sound waves can do