Intensity representation 1

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Intensity representation1

• Representation of the intensity of sound
• (or is it something else about efficiency?)

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Resolution and efficiency
Broad filter
standard listener
Inefficient listener
Threshold- 20 log m
Threshold
Poor temporal resolution
Inefficient listener
standard listener
Notch Width (?f/f)
Modulation Frequency (Hz)
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Contributors to inefficient listening

• Intensity resolution
• Inattentiveness
• Listening strategy
• Physiological noise

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Problem with measuring intensity resolution

• How do you separate bad performance from bad
  resolution?

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Resolution and efficiency
Broad filter
Poor resolution
Inefficient listener
Threshold
Dont know
Threshold
standard listener
standard listener
Notch Width (?f/f)
Stimulus
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Topics in intensity processing

• Absolute sensitivity
• Intensity discrimination
• Loudness

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Prenatal absolute sensitivity measurement
problems

• What is the stimulus that reaches the fetal ear?
• What is the stimulus that reached the fetal inner
  ear?
• What is the message in the fetal auditory nerve?
• Is the response to the sound or to the maternal
  response?

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Lecanuet et al. (1988)

• 37-40 wk gestational age fetuses
• 500, 2000, 5000 Hz octave bands of noise
• Speaker 20 cm above maternal abdomen (mother
  listens to music)
• 100, 110, 115 dB SPL 1 cm above maternal abdomen
• 5 second duration
• 5-15 min interstimulus interval
• High (awake) and low (asleep) HR variability
• Cardiac and motor responses (ultrasound)

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Prenatal cardiac responses to sound
36 28
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Prenatal motor responses to sound
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Weir (1979) Pure-tone thresholds of newborns

• Pure tones 125-4000 Hz, various intensities
• Delivered with insert phones
• Recorded respiration, heart rate and motor
  responses scored as response or not offline
• Sensitivity expressed as d

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Pure tone thresholds of newborns
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Werner Gillenwater (1990) Pure-tone thresholds
at 2-5weeks

• Observer-based method, but without reinforcement
  of infant response
• Tones presented with insert earphones
• Frequencies 500, 1000, and 4000 Hz, various
  intensities

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Pure-tone thresholds of 2-5-week-olds
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Trehub et al. (1991) Thresholds for octave-band
noises, 1.5-3.5 mo

• Observer-based method, with no reinforcement
• 4-kHz noise band alternated from left to right
  speakers
• Observer responded signal or no signal

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Third-octave band thresholds, 1.5-3.5 months
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Olsho et al. (1988) Pure-tone thresholds 3-12
months

• Observer-based method (with reinforcement)
• Adaptive thresholds, 250-8000 Hz
• ear bud earphones

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Pure-tone thresholds 3-12 months
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Thresholds for speech-filtered noise
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Third-octave bands, 6 mo-20 yr
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Development of the audibility curve Summary
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Intensity discrimination Adults and children
Which one is more intense, 1 or 2?
Amplitude
When did the increment occur, 1 or 2?
Amplitude
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Intensity discrimination Infants
Respond when the intensity changes
gated
Amplitude
Time
Respond when the intensity changes
Amplitude
continuous increment detection
Time
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Intensity discrimination infants and children
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Detection in noise parallels intensity
discrimination
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Detection in noise in standard psychophysical
procedure
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Evidence for immature resolution v. other sorts
of efficiency?
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Increment detection Infants
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Increment detection Children
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Intensity discrimination Summary

• Intensity jnd improves from about 5-7 dB at 6
  months to 1-2 dB in adulthood.
• Intensity jnd is mature by about 5-6 years of
  age.
• Detection in noise follows the same time course
  as intensity discrimination.
• There is some evidence that intensity resolution
  is poorer during development for low-frequency
  sounds.

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Loudness
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Reaction time as a measure of loudness
Reaction time (ms)
Intensity
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Loudness Infants
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Loudness Children
Line length
Intensity
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Loudness Children
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Loudness discomfort levels Children
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Loudness discomfort levels
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Intensity representation Summary

• Absolute sensitivity at high frequencies is adult
  like in the preschool period, but at low
  frequencies continues to mature into the school
  years.
• Intensity discrimination is mature by 5-6 years,
  and there is a little evidence indicating
  immature intensity resolution in infants and
  toddlers.
• Loudness may grow faster with increasing
  intensity in infants than adults, but loudness
  growth is mature by 4 years.