1. Sound
    • More than what is heard
    •    form of energy which is transmitted through a medium by particles
  2. source
    anything that vibrates or oscillates to generat a sound wave
  3. medium
    • anything made of molecules through which vibration passes
    • sound wave travels through collection of molecules 
    • allows sound wave to reach receiver
    • different mediums have dif densities
    • some examples include:
    •     bull horn
    •     desk
    •     wall etc.
    • the more compact the better to hear
  4. what is medium density and what does it determine?
    • degree to which molecules are closely packed
    •     higher density medium
    •       solid
    •     lower density medium
    •       gas
  5. what is the typical medium for hearing?
  6. what is needed for sound
    • vibration
    • periodic-consistent movement over time
    • aperiodic-irregular movement over time
  7. receiver
    anything that can detect vibration
  8. How does sound travel?
    • particles are displaced slightly from rest
    • air particles are elastic and want to return to rest
  9. displacement
    • change in the spatial position of an object (ie moving an object out of its natural or normal position)
    •     -trace the distance the object moves
    •     -must specify direction object moves in
  10. mass
    represents that in an air particle
  11. spring
    elastic restoring force, force used to get mass back to rest position
  12. elasticity
    object's resistance to change-spring will resist being stretched or shortened
  13. How does sound travel?
    • think of air or any medium as a mass-spring system chained together
    • elastic restoring forces (the springs) keep the particles at equal average distances
    • when an outside force starts the particles in motion, the masses closest to the source move out of rest position and go past rest position to a maximum displacement
    • as they hit their max, the first set of particles hit into the next row of particles, setting them into vibration
    • the second row of particles move out of rest position toward the third row of particles
    • the first row of particles head back to rest position because of elastic recoil force
    • but they do not stop at rest position because of inertia and head to a negative max displacement
  14. what don't the air particles do in relation to how sound travels
    the air particles do not move far from rest position, and do not directly travel from the source to the listener
  15. rarefraction
    • the troughs in the sine wave
    • particles move farther apart
    • regions of lower molecular density
    • air pressure less than atmosphere
  16. condensation
    • compression
    • hill in the sine wave
    • come together
    • regions of higher molecular density
    • air pressure greater than atmosphere
  17. longitudinal propagation
    • direction that a sound travels is the same in which the individual molecules vibrate
    • in contrast to transverse prop which looks like dropping a pebble into a pond (perpendicular to the direction of the waveform)
  18. propagation velocity
    • how fast disturbance moves through medium
    •     speed
    • depends on characteristics of medium
    •     density
    • directly related to density
    •     density increases, prop vel increases
    •     density decreases, prop vel decreases
  19. in what direction does the wave travel in the air?
    in the same direction as the vibrating source
  20. wavelength
    • distance from one point of max condensation to the next max point of condensation
    • directly linked to prop vel but inversely linked to freq
  21. simple harmonic motion
    • SHM
    • sine wave rare in real life
    • a tone of one frequency can be described by  
    •     -freq   
    •     -amplitude   
    •     -phase
    • systems that vibrate with SHM:
    •     pendulums
    •     mass on a spring
    •     tuning forks
  22. linear projection
    circular movement of SHM in a one-dimensional view
  23. repetitive linear motion
    • basic component to sound
    • constat velocity of movement between two points
    • common type of vibration
    • simple harmonic motion SHM
    •     most basic form of repetitive motion
  24. how is an object moving with SHM moving?
    • in a circle at a constant speed
    • uniform angular velocity
  25. frequency
    • sine wave is periodic, repeats itself exactly in equal intervals of time
    •     -period-time necessary to complete one cycle
    •           -unit-sec, millisec etc
    •     -freq-reciprocal of period (F=1/T)
    •           -how many cycles fit in a period of time=freq
    •           -freq=cycles/sec
    •           -unit-Hz=1 cycle/1s
  26. amplitude
    • displacement of the particle-changes sinusoidally over time
    • refers to strength or magnitude of the sound
    • usually measured as sound pressure level
  27. phase
    • starting phase-displacement in degrees from 0 at the instant that vibration begins
    • sine wave- displaced across 360 degrees in a circular motion
  28. period
    • time it takes to complete one full cycle of vibration
    • always measured in unit of time and denoted by T
  29. period and frequecy are...
    • inversely related
    • when period increases and gets longer, freq decrease and gets lower

    when period decreases and gets shorter, freq increase and gets higher
  30. starting phase
    • four ref points located at different angles
    • when wheel begins to tun, each point rotates around circumference with same amp and freq as others
    • only dif among the four waves=angle of rotation at start of time
  31. 0*
    Image Upload 10*
  32. 90*
    Image Upload 2
  33. 180*
    Image Upload 3
  34. 360* or 0*
    Image Upload 4
  35. complex waveforms
    • most waveforms contain more than one freq and are thus called complex
    • combo of two or more sine waves
  36. summation
    • addition of two in-phase sine waves or identical freq and phase
    • result-
    •     -sine wave of equal freq and phase
    •     -amp equals simple sum of component waves
  37. cancellation
    • addition of two sine waves of identical freq and amp but with 180* phase dif
    • result:
    •     wave completely cancelled 
    •     silence
  38. types of complex waveforms
    • complex periodic
    • nonperiodic (1) continuous, (2) transient
  39. spectrum
    • represents freq of sine wave components of the complex wave by their amplitude
    • fundamental freq - f0 - lowest possible sine wave component
    • F0=first harmonic (H1)
  40. Fourier analysis
    • type of spectrum- amplitude spectrum
    • used to analyze complex waveforms into their sine wave components
    • FFT - fast fourier transform
    • displays:
    •     -waveform: time by amp (time domain)
    •     -spectral: freq by amp (freq domain)
  41. FFT
    • Fast fourier transform
    • assess freq and amp components of speech sounds
    • periodic signals
    •     -vowels: line spectrum
    • aperiodic signals
    •     -consonants (obstruents): continuous spectrum
  42. resonance
    • defined as the vibration at the max amp
    • freq dependent - objects resonate best at their natural freq
    • in vocal tract -  change shape of upper vocal tract to preserve some of the laryngeal source freq and allow other to weaken
  43. damping
    • sound is eventually damped (decay of amp over time)
    • resistance: causes the sound to be damped
    •     -frictional resistance
    • high damping and low damping systems
  44. what are psychoacoustics
    • branch of experimental psychology
    • study of changing parameters of auditory stimuli
Card Set
Dr. Spruill Summer 2013