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An explanation of the effects of hearing aids and cochlear implants, using an audiogram
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Understanding the effect of hearing aids and cochlear implant
Roberto Ballerini
audiogram
You all already saw an
audiogram!
audiogram
It is usually used to
visualize a hearing loss
audiogram
A mild one as this…
audiogram
…or a profound one as
this
audiogram
It is perhaps more simple
to understand it
upside-down
audiogram
Now the louder sounds
are up!
audiogram
And the sounds we can
hear are over the red
line
audiogram
With my mild deafness
on high frequencies, I
hear well almost all
speech sounds
audiogram
The right ear of my
daughter only hears an
airplane taking off at
20 meters!
cochlear implant
The effect of the
implant:
do notice that some low
and high frequencies are
missing
cochlear implant
Do remember that young
people can hear from 20
to 20,000 Hz
cochlear implant
Audiometries, instead,
usually test from
125/250 to 4,000/8,000 Hz
cochlear implant
Luckily the main
informative content of
speech is in the central
part!
hearing aids
Left ear of my daughter
hears slightly better!
hearing aids
She can wear
a hearing aid!
hearing aids
Cochlear implant is a
sound synthesizer: it
generates acoustic
sensations
hearing aids
Hearing aids are
amplifiers: they make
stronger the weaker
sounds
hearing aids
Implant lowers our red
line
hearing aids
Hearing aids raise the
weaker sounds in our
audiogram
hearing aids
Whispers raise from 20
to 80 dB, as an example
hearing aids
I stretched it a bit too
far… my daughter
can’t hear whispers
hearing aids
But she’ll hear a good
share of the speech
banana sounds
hearing aids
Warning: I made a
simplification!
hearing aids
I moved up the banana
the same quantity at
every place!
hearing aids
Modern hearing aids can
change its shape…
hearing aids
Giving a higher
amplification where my
hearing is worst
hearing aids
Second simplification: I
amplified strong and
weak sounds the same
way
hearing aids
I can’t really do it:
I’d break the eardrum!
hearing aids
So if a sound is already
strong, I don’t amplify
it!
hearing aids
The airplane stays at
the same place. The
whispering goes up near
the airplane!
hearing aids
So the real effect is
similar to this:
hearing aids
If the hearing loss is
severe or profound, I
need to amplify a lot
hearing aids
And if I amplify a lot
the weak sounds and not
at all the strong ones…
hearing aids
The difference that I
perceive between strong
and weak sounds is a lot
weaker
hearing aids
Last peculiar case: I
have a «hole» at some
frequency
hearing aids
Digital hearing aids can
«move» the sound
frequency
hearing aids
If I miss the high, I move
them towards lower
frequencies!
hearing aids
Like that !!!
