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Hearing & Aging
Or age brings wisdom and other bad
news
Presbyacusis
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Age-related hearing loss
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Degeneration of the inner ear
Largest decline over 2kHz
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Low frequency hearing relatively
unaffected
Incidence
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100% of population will develop
minimal hearing loss
30% over 65 & 40% over 75
moderate to severe hearing loss
Gender Affects Hearing
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Presbyacusis & Gender (Jerger et al., 1993)
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Female hearing

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Degrades 2 dB HL per decade
Larger deficits below 1 kHz than men
 Cause?
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Male hearing

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Degrades 3 dB HL per decade
Largest deficits above 1 kHz
 Noise induced threshold shift
Cause of Presbyacusis

Central/cortical
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Evidence
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Deficits in multiple sensory systems
Correlated cross-sensory degradation
Histological support counter claim
Cochlear
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Evidence
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ABR highly latent to acoustic stimulation
Change in Outer Hair Cell functioning
 Otoacoustic emissions decrease with age, higher
threshold
 (Outer hair cell generated sound)

Change in inner hair cell density
 Reduced hair in the initial 1/3 of basilar membrane
 Why should more high freq. hair cells be damaged?

Change in basilar membrane stiffness
More bad news: Recruitment
Loudness recruitment
DEMO

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Outer hair cell dysfunction
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All or nothing
Normal outer hair cell response
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Non-linear gain control
Loudness recruitment
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Latent response to stimulation
Increased threshold
Sudden engagement
Temporal Synchrony
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Phase coding of auditory stimuli
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MacDonald et al., (under review)
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Normal: lock to wave peaks
Older: Phase locking inconsistencies
Compare sentence comprehension of
younger adult ‘jittered’ speech with
normal older adults
DEMO JITTERED SPEECH

Equal performance across age groups

Replicates findings in speech paradigms
Effects of Age-related Hearing Losses
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Signal processing load


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Normal hearing: auditory restoration and
processing
Older hearing: increased demand for auditory
restoration and processing
‘Cascade Up’
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Greater effort for hearing
Decreased resources/efficiency


Effects speeded processing, multiple operations
Berlin Aging Study (Baltes & Lindenberger, 1997)
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Majority of cognitive aging = sensory degradation
Studies of Speeded Speech
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Older vs. Younger adult (Schneider et al., under
review)
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Three methods of speeding speech


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
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Increasing tape speed
Removing every third 10 ms segment
Reducing steady-state formants by 90%
How will younger and older adults respond?
Method of speeding speech causes
age-related differences

Actual speed does not affect older adults