Recent Advances in Hearing Health Care and Research - What's Next? Pt 1


Uploaded by DeafnessResearchFdn on 07.10.2010

Transcript:
The Deafness Research Foundation is the nation’s oldest charity, raising money for hearing
research. Many of the advances you enjoy today came about as the result of DRF funding in
the past. [pause]
As Helen Keller said, she was both blind and deaf, she said hearing is much more important
than vision because hearing separates you from people, vision separates you from things.
It is a language problem. You can talk to a blind person but it is very hard to talk
to a deaf person who doesn’t read lips. And there is a lot more money spent on vision
research than there is on hearing research. [pause]
Most people don’t know they have hearing loss because it begins so gradually. There
are conditions where it can come out over night. Your spouses know when your husbands
can’t hear you. And I want to talk about that. Hearing is always poor in a noisy place
and certainly this is a noisy place so if you can’t hear me then just raise your hand
and I will scream a little louder. [pause] One of the problems we have is that people
regard hearing loss as inevitable and that it is just one of those things that we can’t
do much about it. Well, that certainly has been true in the past but now days with the
improvements in hearing aids and surgeries for hearing loss we have a new attitude. Hearing
aids will help most people but amazingly only about 1 in 5 persons who could benefit from
a hearing aid has one. That is in part due to the fact that they are so expensive. [pause]
Now cochlear implants, the cochlea is the inner ear. I will show you a picture of that
later. They are wonderful and have been around about 25 years. When your hearing is so bad
that a hearing aid won’t work a cochlear implant will work 95 times out of 100. Every
now and then, we can cure somebody’s hearing problem but for the majority of people we
just have to treat it in one way or another. But on the horizon regeneration of hearing
is coming down the path. So I want to talk to you about things in the past, things that
we have now, and some things in the future. [pause]
We will spend just a minute talking about the way the auditory system is built and how
it functions. It is a complex system. We listen with our ears but we hear with our brains.
So everything from here to here [pointing at ear and head] is involved in hearing. If
you are familiar with the four parts, the outer ear gathers the sound, the middle ear
conducts the sound, the inner ear interprets the sounds and transforms it into electrical
impulses, and then the brain has central pathways that interpret the sounds. Sound is nothing
more than vibration so here we have a tuning fork and these pressure waves actually go
and move your ear drum. When we talk about hearing we have to talk about both its loudness,
which is on the vertical scale here. Sorry my pointer is not working. And frequency.
Now going across the top, 4,000 is the top note on a piano and my voice is down around
the 200 cycles per-second range. The loudness you see at the bottom, a jet plane is at 110
decibels. Well, guess what the sound level in this room is and in this hallway? We’re
78 decibels. So I could shout at 90 DB. You don’t want me to do that. So I’ve only
got 12 DB between shouting and you being able to hear me. [pause]
Ok, the letters on the alphabet are where the speech sounds are heard. And look on the
right side. The T, H, F, and S are very difficult sounds to hear when you have hearing loss.
So you can’t tell ‘th’ from ‘fa’ from ‘sa’ as distinct sounds. That’s
why people say ‘I can hear you but I can’t understand you.’ There are several reasons
for that. One of which is that most hearing loss is high frequency and that’s where
the consonants are heard. So to look at the ear, we start at the big section on the left
and hone down into progressively smaller and smaller sections. The outer ear, this thing
lets the sound into your head and the ear drum vibrates and the three little bones [pause
walks over to power point].
The ear drum and the three little bones transmit
the sounds in the inner ear [pause]
So what part of the ear is stimulated depends on its frequency. A high pitched sound like
2,000 is way down here and a low pitched sound is at the tip so this allows the ear to analyze
the frequency of sounds coming into it. [pause walks over to podium]
I think I better stick up here. In yellow we have the balance part of the ear and in
blue the hearing part. They’re part of the same system. [pause]
And in the cochlea, or the hearing part, we have two fluid spaces. The one in the middle
is a positive electric charge that powers the hearing mechanism. [pause]
The hair cells are what makes the ear work. They are unique. They are not in any other
part of the body. They detect the wave motion and actually convert the energy into nerve
impulses. So you see here the inner ear cell on the right is where the sound is actually
connected to the brain. And for years the three outer hair cells, we [scientists] were
puzzled as to what they do. We now know that these are actually little amplifiers that
make the sound bigger when they are stimulated. So when a sound comes through and the membrane
moves up and down, the hair cells will actually contract and make the sound louder. Here we
are looking down on the top of the three rows of outer cells in a V configuration [referring
to powerpoint] and the inners are at the top. This slide shows the difference between the
inner and outer hair cells. Both of them need an electoral current in the ear to make them
work. When the power cells in our ear decline with age then there is less energy to make
the hearing mechanism work [coughs].
It is true that for something to be sensitive this also makes it very susceptible to damage
and loud sounds in our environment, once it gets over 90 DB, it will actually start damaging
the system. It does it by knocking out the hair cells at the 4,000 cycle range….