Intensity representation 1 Representation of the intensity of sound (or is it something else about efficiency?)

Resolution and efficiency Threshold Notch Width (∆f/f) Broad filter Inefficient listener “standard” listener Threshold- 20 log m Modulation Frequency (Hz) “standard” listener Inefficient listener Poor temporal resolution

Contributors to inefficient listening Intensity resolution Inattentiveness Listening strategy “Physiological” noise

Problem with measuring intensity resolution How do you separate bad performance from bad resolution?

Resolution and efficiency Threshold Notch Width (∆f/f) Broad filter Inefficient listener “standard” listener Threshold 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) 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

Weir (1979): Pure-tone thresholds of newborns Pure tones 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

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, 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, months

Olsho et al. (1988) Pure-tone thresholds 3-12 months Observer-based method (with reinforcement) Adaptive thresholds, Hz “ear bud” earphones

Pure-tone thresholds 3-12 months

Thresholds for speech-filtered noise

Third-octave bands, 6 mo-20 yr

Development of the audibility curve: Summary

Intensity discrimination: Adults and children Amplitude Which one is more intense, 1 or 2? Time Amplitude When did the increment occur, 1 or 2?

Intensity discrimination: Infants Amplitude Respond when the intensity changes Time Amplitude Respond when the intensity changes “gated” “continuous” “increment detection”

Intensity discrimination: infants and children

Detection in noise parallels intensity discrimination

Detection in noise in standard psychophysical procedure

Evidence for immature resolution v. other sorts of efficiency? Threshold Stimulus “standard” listener Poor resolution Don’t know

Increment detection: Infants

Increment detection: Children

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 Reaction time (ms)

Loudness: Infants

Loudness: Children Intensity Line length

Loudness: Children

Loudness discomfort levels: Children

Loudness discomfort levels

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.