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Intensity representation 1 Representation of the intensity of sound (or is it something else about efficiency?) Resolution and efficiency Broad filter “standard” listener Inefficient listener Threshold- 20 log m Threshold Poor temporal resolution Inefficient listener

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intensity representation 1

Intensity representation1

Representation of the intensity of sound

(or is it something else about efficiency?)

resolution and efficiency
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)

contributors to inefficient listening
Contributors to inefficient listening
  • Intensity resolution
  • Inattentiveness
  • Listening strategy
  • “Physiological” noise
problem with measuring intensity resolution

Problem with measuring intensity resolution

How do you separate bad performance from bad resolution?

resolution and efficiency5
Resolution and efficiency

Broad filter

Poor resolution

Inefficient listener

Threshold

Don’t know

Threshold

“standard” listener

“standard” listener

Stimulus

Notch Width (∆f/f)

topics in intensity processing
Topics in intensity processing
  • Absolute sensitivity
  • Intensity discrimination
  • Loudness
prenatal absolute sensitivity measurement problems
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?
lecanuet et al 1988
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)
weir 1979 pure tone thresholds of newborns
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’
werner gillenwater 1990 pure tone thresholds at 2 5weeks
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
trehub et al 1991 thresholds for octave band noises 1 5 3 5 mo
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”
olsho et al 1988 pure tone thresholds 3 12 months
Olsho et al. (1988) Pure-tone thresholds 3-12 months
  • Observer-based method (with reinforcement)
  • Adaptive thresholds, 250-8000 Hz
  • “ear bud” earphones
intensity discrimination adults and children

1

1

2

2

Time

Time

Intensity discrimination: Adults and children

Which one is more intense, 1 or 2?

Amplitude

When did the increment occur, 1 or 2?

Amplitude

intensity discrimination infants
Intensity discrimination: Infants

Respond when the intensity changes

“gated”

Amplitude

Time

Respond when the intensity changes

Amplitude

“continuous”

“increment detection”

Time

evidence for immature resolution v other sorts of efficiency

Poor resolution

Don’t know

Threshold

“standard” listener

Stimulus

Evidence for immature resolution v. other sorts of efficiency?
intensity discrimination summary
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.
reaction time as a measure of loudness
Reaction time as a measure of loudness

Reaction time (ms)

Intensity

loudness children
Loudness: Children

Line length

Intensity

intensity representation summary
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.