Intensity representatio n 1 Representation of the intensity of sound (or is it something else about efficiency?)
Intensity representation
1Representation of the intensity of sound
(or is it something else about efficiency?)
Resolution and efficiencyT
hres
hold
Notch Width (∆f/f)
Broad filter
Inefficient listener
“standard” listener Thr
esho
ld-
20 lo
g m
Modulation Frequency (Hz)
“standard” listener
Inefficient listenerPoor temporalresolution
Contributors to inefficient listening Intensity resolution Inattentiveness Listening strategy “Physiological” noise
Problem with measuring intensity
resolutionHow do you separate bad
performance from bad resolution?
Resolution and efficiencyT
hres
hold
Notch Width (∆f/f)
Broad filter
Inefficient listener
“standard” listenerT
hres
hold
Stimulus
“standard” listener
Poor resolution
Don’t know
Topics in intensity processing Absolute sensitivity Intensity discrimination Loudness
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) 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)
Prenatal cardiac responses to sound
36 28
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’
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
Pure-tone thresholds of 2-5-week-olds
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”
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
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
Am
plitu
de
Which one is more intense, 1 or 2?
Time
1 2
Time
1 2
Am
plitu
de
When did the increment occur, 1 or 2?
Intensity discrimination: InfantsA
mpl
itude
Respond when the intensity changes
Time
Time
Am
plitu
de
Respond when the intensity changes
“gated”
“continuous”“increment detection”
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?
Thr
esho
ld
Stimulus
“standard” listener
Poor resolution
Don’t know
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.
Loudness
Reaction time as a measure of loudness
Intensity
Rea
ctio
n tim
e (m
s)
Loudness: Infants
Loudness: Children
Intensity
Line
leng
th
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.