Auditory Sensitivity

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Auditory Sensitivity

• MAP MAF
• dB HL
• dB SL

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MAP
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MAF
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dB Hearing Level (dB HL)

• Based directly on MAP
• Used in hearing testing
• Converting between SPL and HL
• SPL to HL
• Subtract correction factor
• HL to SPL
• Add correction factor

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dB Sensation Level (dB SL)

• Refers to the number of dB that a stimulus is
  above or below an individuals threshold.
• An individuals threshold is always 0 dB SL
• e.g., An individual has a 25 dB HL loss at 1000
  Hz. This now becomes 0 dB SL.
• If we present a sound at 40 dB SL to this person,
  where do we set the HL dial on the audiometer?

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Masking

• Generic definition
• Interference of one stimulus by another.
• Operational definition
• Process by which the threshold of audibility for
  one sound is raised by the presence of another
  (masking) sound.

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Masking

• Cross Hearing
• The ability to hear a stimulus in the ear
  opposite the test ear, that is, the non-test ear.
• Interaural Attenuation
• The amount of sound attenuation that occurs as
  the signal passes from the test ear to the
  contralateral cochlea.

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Example of cross hearing and interaural
attenuation
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Effect of a masking noise.
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Binaural Hearing

• Localization
• Binaural Squelch
• Binaural Summation
• Precedence Effect

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Localization

• Interaural time differences
• Interaural level differences

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Polar plot showing IATD IALD
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Mechanism used to Localize
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Binaural Squelch

• Ability to suppress background noise and attend
  to a specific auditory signal.
• Also known as auditory figure-ground.

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Binaural Summation

• Improvement in hearing threshold when compared to
  monaural hearing.
• 3 dB at threshold
• 6 dB at 50 dB
• 9 dB at 90 dB

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Precedence Effect

• Ability to localize or identify signal in a
  reverberant field.
• Takes first waveform and suppress any echoes
  which helps intelligibility.
• Uses first waveform to localize

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Example of Precedence Effect
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Summary