Vibration, Sound, and Hearing 2

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  1. Dynamic Range
    the range of differences between the smallest and largest changes in something
  2. What dynamic rance is our hearing capable of detecting?
    1 - 10,000,000
  3. what scale is often used to compress the dynamic range into more manageable figures?
    the logarithmic scale
  4. the decibel
    a dimensionless unit used to compare the ratio of two quantities
  5. the decibel is usually used in relation to what type of energy?
    Acoustic energy, such as sound pressure, power, and/or intensity
  6. decibel notations
    • dB-SPL - (acoustic) sound pressure level
    • dBm - electrical power
    • dBv/dBu/dBV - electrical voltage
  7. is the decibel a simple or accurate representation of perceived loudness?
    not necessarily
  8. doubling sound pressure results in an
    increase of 6 dB
  9. doubling the measurement distance results in
    a decrease of 6 dB
  10. doubling sound power results in an
    increase of 3 dB
  11. adding two similar (but uncorrelated) sounds at the same level generally produces an
    increase of about 3 dB-SPL
  12. Equal Loudness Principle
    • Auditory sensitivity varies with frequency
    • Our hearing mechanism is less sensitive to low and high frequencies then mid-range frequencies
    • These sensitivity differences lessen as loudness increases
    • One reason why people think loud music "sounds better"
  13. Phon (pernounced fone)
    unit used to express the perceived loudness level as related to the ear's subjective impressions at various frequencies
  14. What is a more appropriate presentation of simple loudness than the decibel?
    • Phon
    • the decibel describes intensity more than loudness
  15. sound pressure level at 1000 Hz.
    Phon level
  16. is the Phon a simple or accurate representation of perceived loudness?
    not nexessarily
  17. Equal Loudness Contours
    Image Upload 1
  18. Sone
    • perceived loudness
    • unit used to express comparative loudness of multiple sounds
    • arbitrary scale created to provide a linear representation of perceived loudness
    • 1 sone = 40 phons
    • every 10 phons (10x intensity) = 2x sones
  19. The Auditory System
    Image Upload 2
  20. outer ear
    accentuates consonants
  21. middle ear
    impedance match to inner ear
  22. inner ear
    frequency and intensity analysis
  23. brain stem
    combines signals from both ears
  24. brain
    integrates all of the signals
  25. premature hearing loss
    hearing damage caused by exposure to loud sounds varies with loudness, frequency, duration, and exposure time
  26. how does prolonged exposure to dangerous noise levels affect the auditory system?
    • prolonged exposure decreases auditory sensitivity
    • raises the threshold of hearing (middle ear)
  27. TTS - Temporary Threshold Shift (aka auditory fatigue)
    • creates a false perception of actual loudness
    • necessitates compensation (turning the volume up even more)
    • could last minutes, hours, or days
  28. Tinnitus
    • ringing, whistling, or buzzing in the ears after prolonged exposure to loud sounds
    • could last minutes, hours, or days
    • indicates damage is either imminent or has already occured
  29. PTS - Permanent Threshold Shift
    Permanent hearing loss
  30. hearing loss is more pronounced in which frequency range
    high frequency sensitivity
  31. masking
    the obscuring of one sound (or aspect) by another
  32. pure tones close in frequency mask each other more easily than
    widely-spaced tones
  33. pure tones mask ______ frequencies more easily than ______ frequencies
    high, low
  34. which tones can mask broader range of frequencies?
    louder tones
  35. which bands of noise mask like pure tones?
    narrow bands
  36. forward masking
    an initial tone can mask a subsequent tone, even if it has stopped and the two do not overlap in time
  37. backwards masking
    a tone that begins shortly after another can mask the first
  38. central masking
    tones heard by one ear can be masked by tones in the other
  39. binaural hearing (sound localization)
    • hearing with the use of two ears
    • inter-aural intensity differences
    • inter-aural timing differences
    • affected by wavelength (frequency)
  40. Precedence effect
    directed sounds reached our ears first and indirect sounds interact with reflective objects before being heard
  41. how closely must sounds reach our ears to be perceived as coming from the same direction?
    20 milliseconds or less
  42. localization becomes difficult as
    the time difference increases
Card Set:
Vibration, Sound, and Hearing 2
2012-12-20 16:01:19

2055 final
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