Hearing loss support - Newsweek article

Author

Newsweek article

Steve

2005-06-01, 11:51 am

Excerpts from http://www.msnbc.msn.com/id/8017906/site/newsweek

More than 28 million Americans currently have some degree of hearing
loss, and the number is expected to soar in the coming years, reaching
an astounding 78 million by 2030.

One study estimates that as many as 5.2 million children in the United
States between age 6 and 19 have some hearing damage from amplified
music and other sources.

Thanks to their years of living loudly, many boomers are ahead of
schedule when it comes to hearing loss, showing symptoms in their late
40s and 50s.

Most common types of hearing loss occur at the higher frequencies and
are caused by damage to hair cells. Slattery describes the cochlea as
"a piano, with 15,000 keys rather than 88." Different parts of the
cochlea process different frequencies of sound, so when you have
hearing loss at a certain frequency, it's as if that part of the
keyboard is not functioning.

Various levels of noise affect hair cells in various ways. If a
rocket-propelled grenade goes off right next to you, you can
experience "acoustic trauma" that kills hair cells and causes the
instant loss of a great deal of hearing.

Hanging out directly in front of the speakers at a Green Day concert
could result in a less serious "temporary threshold shift," in which
the hair cells are stressed but not permanently damaged. Such stress
is often accompanied by ringing in the ears that can last for hours or
even days. Repeated threshold shifts can lead to permanent hearing
loss.

And then there's what might be called noisy-world syndrome. While an
individual's noise exposure may not reach the official danger zone,
the worry is that the chronic din of daily life could lead to
deterioration over time. "There's not a lot of data about it," says
Rabinowitz, "but our concern is that there is less and less time for
the ears to rest, and so the hair cells are going to be prematurely
exhausted."

Protecting your hearing starts with understanding how noise works. The
classic formula for assessing the risk of hearing loss is the
intensity of the noise, measured in decibels (the danger starts at 85
decibels, roughly the sound of a lawn mower), multiplied by duration,
the time of exposure. In other words, the louder the noise, the less
time you should be exposed to it.

Prolonged exposure to any noise above 85 decibels can cause gradual
hearing loss. For each five-decibel increase, the permissible exposure
time is cut in half. So one hour at 110 decibels is equivalent to
eight hours at 95 decibels. And sound levels above 116 decibels
(snowmobiles are about 120, rock concerts about 140) are unsafe for
any period of time.

In a recent informal study at the House Ear Institute, researchers
found that the new generation of digital audio players, with their
exceptional clarity, allow listeners to turn up the volume without the
signal distortion that occurs with traditional analog audio. Without
distortion, which serves as kind of natural volume governor, listeners
may be exposed to unsafe sound levels without realizing it. In
preliminary observations, the music at the eardrum topped 115
decibels. Exposure to noise that loud for more than 28 seconds per
day, over time, can cause permanent damage.

A new generation of implantable and semi-implantable hearing aids is
currently being developed and tested. Unlike conventional aids, the
new devices transmit sound vibrations directly to the bones in the
middle ear, bypassing the eardrum and improving speech perception.
"You can amplify the higher frequencies without feedback problems,"
says Slattery, "and that gives a richness to the sound. It's the high
frequencies that help you localize sound and hear better in noisy
situations."

Other pluses: no clogged ear canal and no visible sign of infirmity.
But until insurance companies start paying for hearing aids (they are
under increasing pressure to do so), the $15,000+ devices will remain
out of reach for most.

A more permanent solution to hearing loss - regenerating damaged
cochlear hair cells - is the shared goal of a scattered band of
researchers around the country. Researchers at the university of
Michigan have used gene therapy to grow new hair cells in guinea pigs.

At the House Ear Institute, Andrew Groves and Neil Segil are studying
the embryonic development of hair cells in genetically engineered
mice. If they can unravel the process, figure out how it starts and
why it stops in mammals, they may eventually be able to reactivate the
cells and have them make new hair cells. In a related experiment, they
have managed to coax some embryonic cochlear cells in mice to restart
and become hair cells.

Kellie J. Berger

2005-06-02, 10:54 pm

?? on the digital audio players... if a hearing impaired child were to
listen to something like this thru his/her T-coil and a loop, would the
decibel level at the eardrum likely be the same? Assuming they have the HAs
set to damper too loud noises. (don't remember what this is called, but like
an automatic volume control)

--
-- Kellie
kjbeanne at yahoo dot com
www.kjbeanne.com/kellie.htm

"Steve" <upg@knf.inv> wrote in message
news:urfr911aqbeoqpgldem3okcqihfc5vmcm4@4ax.com...
>
> Excerpts from http://www.msnbc.msn.com/id/8017906/site/newsweek
>
>
>
> In a recent informal study at the House Ear Institute, researchers
> found that the new generation of digital audio players, with their
> exceptional clarity, allow listeners to turn up the volume without the
> signal distortion that occurs with traditional analog audio. Without
> distortion, which serves as kind of natural volume governor, listeners
> may be exposed to unsafe sound levels without realizing it. In
> preliminary observations, the music at the eardrum topped 115
> decibels. Exposure to noise that loud for more than 28 seconds per
> day, over time, can cause permanent damage.
>