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 !!!

Thanks!!

Roberto Ballerini

roberto.ballerini.work@gmail.com