# sound and its measurements

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1. sound
• a compressional wave that can be described as
• 1) psychologically aka an auditory experience
• 2) physically- a series of disturbances of molecules
2. Vibration
the principle prerequisite for sound
3. vibration is affected by
• the transmitting medium and sound source.
• the medium most have mass and elasticity
4. elasticity
the ability of an object to resist changes in shape or volume. The more densely packed molecules the more springier.
5. Tuning fork Pitch
• Pitch is consistent when striking a tuning fork.  The only variables that change are the vibrations(amplitude) and the loudness.
• - mass and elasticity dictates how the fork osscilates
6. Tuning fork motion
• At rest the tuning fork has kinetic energy
• at the centre and beyond resting the tuning fork has potential energy
7. Pure tones
the simplest of all sound waves
8. sine waves
allow us to represent a sound wave mathematically
9. sine waves described in 3 ways
• 1)phase
• 2)amplitude
• 3)frequency
10. Phase as a circle
used to describe the starting position of the sound or the phase relationship between 2 or more sounds.  Can have the same amplitude and frequency but different phases
11. We use phase for
Localization
12. constructive interference
13. destructive interference
is when two sine waves cancel each other out resulting in no signal.  This happens when sine waves start at opposite phases
14. amplitude
measures of strength and magnitude of sound wave.  Measures in sound pressure. It relates to the force being applied to the source
15. peak to peak
maximum peak to maximum trough measurement
16. root mean square amplitude
the average of many points on a sine wave
17. Frequency
the rate at which a sine waves repeats itself over time. How much does it vibrate per second? f=1/T T=1/F
18. Hearing ranges for normal hearing
20 hz to 20,000 but our best hearing is 1000-4000 Hz. Hearing tests show sensitivities from 250 Hz to 8000 Hz
19. Speed of sound
• -influenced by the temperature and how dense the medium is. The tighter the molecules are packed the faster sound can travel.
• -not related to hertz
20. wavelength and frequency
• inverse relationship. When wavelength increases freq decreases and when freq increases wavelength decreases
• -as speed of sound increases the wave length increases
21. The longer the wavelength of a sound wave
the thicker a walls needs to be to attenuate it.  When we test normal hearing at 20Hz we need to be in a room with thick walls.
22. stationary source
the frequency does not change so we hear the same pitch
23. moving source
as it approaches you the pitch gets higher then lower as it passes you (doppler affect)
 Author: Wesleypjones ID: 316350 Card Set: sound and its measurements Updated: 2016-02-23 04:07:10 Tags: sound its measurements Folders: Description: sound and its measurements Show Answers: