sound and its measurements

  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
  12. constructive interference
    two sine waves add together
  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)
Card Set
sound and its measurements
sound and its measurements