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

Fundamental frequency A guitar string = ½ a wavelength L 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 Frequency is inversely proportional to wavelength Pendulum Lab: http://phet.colorado.edu/en/simulation/pendulum-lab

Longitudinal Sound wave Or Compression Wave Sound wave - visual Visual soundwave https://www.youtube.com/watch?v=s9GBf8y0lY0 Decibles: https://www.youtube.com/watch?v=jCQRBJwUt2s Wave in tub

Harmonics 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 series Standing 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 series Standing 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 tube n = harmonic number L = length of tube

Fundamental frequency is the lowest possible f of a standing wave

Decibels – unit measuring the intensity of sound Exponential scale (logarithm) 0 dB = smallest audible sound 10 dB = 101 threshold of good hearing 20 dB = 102 leaves rustling, ticking of watch 30 dB = 103 whisper 40 dB = 104 quiet library 50 dB = 105 moderate rainfall 60 dB = 106 normal voice; dishwasher 70 dB = 107 busy street traffic 80 dB = 108 vacuum cleaner; alarm clock 90 dB = 109 lawnmower; hair dryer, blender 100 dB = 1010 mp3 player at full volume; lawn mower 110 dB = 1011 front row at a rock concert; car horn 120 dB = 1012 police siren 130 dB = 1013 threshold of pain; jackhammer 140 dB = 1014 military jet takeoff; gunshot; fireworks 150 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 Amplitude – measureable Loudness – human perception, duration, frequency

Any sound above 85 dB can cause hearing loss. Related both to the power as well as length of exposure. 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) http://www.animations.physics.unsw.edu.au/jw/dB.htm#soundfiles

Sound 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 The coolest things sound waves can do https://www.youtube.com/watch?v=Ude8pPjawKI William Tell Overture https://www.youtube.com/watch?v=hxIuIxqo2So https://www.youtube.com/watch?v=uUpDG680uew