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== Frequency/Period == | == Frequency/Period == | ||
Revision as of 18:45, 1 July 2007
Contents
Speed of Sound
The Speed of sound is measured in meters per second.The speed of sound is affected by several factors: temperature, humidity, and elasticity.
SOS ~ 344 m/s or 1130 f/s
NOTE: for class we will assume the speed of sound in air @ 20 degrees Celsius an 75% humidity is 344m/s
Speed of sound Calculator http://www.measure.demon.co.uk/Acoustics_Software/speed.html
Frequency/Period
Sound is a periodic event. This means that there is a fixed amount of time between different events.The Frequency component of a sound wave affects the pitch of the sound.
Frequency is measured in Hertz (cycles per second)
Period = 1 / Frequency in HzT = 1/f
Frequency = 1/ Period f = 1/T
Different types of frequency components periodic/ aperiodic
It is assumed the humans can hear frequencies from 20Hz to 20,000 Hz.
20-20KHz Sweep
- http://iam.colum.edu/sound/media/sweep20-20.wav 41kb,16 bit 3.7megs
Resonance
Tacoma Narrows Bridge
Movie1 http://interactive.colum.edu/sound/media/tacoma3.avi
Movie2 http://interactive.colum.edu/sound/media/tacoma4.avi
Wavelength
Wavelength is measured in distance (ft. of m)
The actual physical length of a single cycle of a wave
Wavelength = speed of sound / Frequency in Hz
- λ = SOS/f
wavelength = speed of sound * period
- λ = SOS*T
The wavelength of a sound wave varies greatly with the frequency of the wave. A 20 kHz wave has a wavelength of 1.72 (0.7 in)cm while a 20 Hz wave has a wavelength of 17.2 m (~56 ft.).
Examples http://iam.colum.edu/MTD2/lectures/week1_examples.htm
Perception of Amplitude and Frequency
Humans do not hear all frequencies equally. We perceive different frequencies with equal energy to have different amplitudes. The Fletcher Munson Curves show the phons scale, how amplitude is perceived by frequency
Fletcher Munson Curves 1 http://arts.ucsc.edu/EMS/Music/tech_background/TE-02/AcNumbers/AcNumbers.html
Fletcher Munson Curves 2 http://www.allchurchsound.com/ACS/edart/fmelc.html
Fletcher Munson Curves 3 http://hyperphysics.phy-astr.gsu.edu/hbase/sound/eqloud.html
Behaviour of sound waves
- Interference and Beats
Music Theory Rhythm
Music Theory time and meter Time
- Time Signatures - wikipedia examples -ie only sorry
- Beats and measures
- Music Theory Online Lesson 4 Time Signatures
- Online Music Theory Reference
Poly Rhythms vai.com
Looping in Sound Forge
- Turn on Loop
- Mark ins and outs
Homework
SuperFresh DJ MC Down Guy
Create three loops of one song and string them together to 'remix a song'.
