# 331 2.1 Pure Sounds : Acoustics

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1. definition of sound
vibrations propagated (produced) in an elastic medium
2. sound has...
serious emotional content
3. sound needs
source of vibration, force, medium, hearing mechanism
4. sound is
a disturbance of particles (atmosphere)
5. condensation
more molecules = more than atmospheric pressure
6. rarefaction
less molecules = less than atmospheric pressure
7. simple harmonic motion
• something constantly repeating itself (as in vibration)
• ex) a circle constantly repeats itself
8. you can not do anything with sound
until you put numbers to it
9. we can talk about sound in relation to
a circle and a sine wave
10. synonym of loudness
intensity
11. synonym of frequency
pitch
12. example of simple harmonic motion
circle
13. to make the sound louder
make the circle bigger using diameter and radius
14. to make the sound softer
make the circle smaller using diameter and pitch
15. to make the pitch higher
rotate the circle faster
16. to make the pitch lower
rotate the circle slower
17. what represents the rotation of the circle
a sine wave
18. sine wave y axis
• Amplitude (volts)
• Amp (v)
19. sine wave x axis
• time (seconds)
• time (s)
20. two aspects of sound to model
• loudness (amplitude)
• pitch (period and frequency)
21. three sound amplitudes
• Peak Amplitude (Ap)
• Peak to Peak Amplitude (App)
• RMS Amplitude (A rms)
22. Ap and App are
instantaneous
23. final amplitude is
an average
24. finding final amplitude
• S - square all #s
• M - median
• R - take square root
25. Arms formula
Arms = .707 x Ap
26. pitch can be described by
pitch or frequency
27. period
• time of 1 cycle of vibration
• units are seconds or milliseconds
28. frequency
• number of cycles per second
• units are Hertz (Hz)
29. Heinrich Rudolph Hertz
• German Physicist
• 1857 - 1894
• investigator of electromagnetic waves
• theory behind radio (tv, cell phones, internet, etc)
30. period and frequency are related
• T = 1/F
• F = 1/T
31. in order to do the period and frequency formulas, time must be in
• seconds
• NOT milliseconds
32. speed of sound depends upon
the medium
33. what determines if the sound will go through an object
wavelength
34. low frequencies go through objects because
their wavelengths are longer
35. wavelength formula
• ^ = c/f
• ^ = wavelength
• c = speed of sound (ft/sec)
• f = frequency
• units = feet / cycle

## Card Set Information

 Author: shanamd2010 ID: 129066 Filename: 331 2.1 Pure Sounds : Acoustics Updated: 2012-01-19 23:40:43 Tags: acoustics Folders: Description: CDO 331 Show Answers:

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