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

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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.