SENSITIVE HEARING Minimum Audible Pressure (MAP) MAP - Increased intensities needed in low and high frequencies
- Low Frequencies:
- Middle Ear Impedance characteristics.
- High Frequencies:
- Hair cell populations in high frequencies are diminished.
MAP - Females have about 3 dB better thresholds than males
- At about age 18 high frequencies begin to decline due to hair cell atrophy at base of cochlea.
- At about age 50, a significant decline occurs at 4000 Hz and above.
MAP - Thresholds for discomfort are about 110 dB SPL across all frequencies.
- Thresholds for pain are about 130 dB SPL.
Minimum Audible Field (MAF) Why the Difference between MAP and MAF - About a 6 dB difference due to …
- Calibration differences between transducers
- Head/body diffraction effects (low freqs)
- Ear canal/concha resonances (high freqs)
- Calibration differences are also responsible for MAP differences between types of earphones (e.g., TDH, insert, circumaural).
dB Hearing Level (dB HL) - Based directly on MAP
- Used in hearing testing
- Important to take calibration differences into account for different transducers.
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.
Masking 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.
Masking - Cross Hearing
- Interaural Attenuation
- The amount of sound attenuation that occurs as the signal passes from the test ear to the contralateral cochlea.
Example of cross hearing and interaural attenuation Effect of a masking noise. Binaural Hearing - Localization and Lateralization
- Binaural Squelch
- Binaural Summation
- Precedence Effect
Localization - Duplex Theory of Localization
Polar plot showing IATD & IALD Neural mechanism used to localize Lateralization - Similar to localization but usually uses earphones to deliver stimulus.
- Perceptually the sound appears to coming from inside the head instead of outside the head (localization).
- Mechanisms
Binaural Squelch - Ability to suppress background noise and attend to a specific auditory signal.
- Also known as auditory figure-ground.
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
Precedence Effect - Ability to localize or identify a signal in a reverberant (echoic) field.
- Takes first waveform and suppress any echoes which helps intelligibility.
- Uses first waveform to localize
Do'stlaringiz bilan baham: |
