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CX2SA > HEALTH 24.06.06 00:26l 71 Lines 3641 Bytes #999 (0) @ WW
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Subj: Noisy ISS may have damaged..
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Sent: 060623/2218Z @:CX2SA.LAV.URY.SA #:15689 [Minas] FBB7.00e $:15689_CX2SA
From: CX2SA@CX2SA.LAV.URY.SA
To : HEALTH@WW
Noisy ISS may have damaged astronauts' hearing
==============================================
Six years after launch, the International Space Station's living quarters are
still noisier than they should be. Now Russian news reports say that astronaut
Bill McArthur and cosmonaut Valery Tokarev returned from their six-month stay
aboard the ISS in April 2006 with some hearing loss.
NASA will not discuss the health of individual astronauts, but spokesperson
Kylie Clem told New Scientist: "It's not an impedance to operations or crew
health or safety. It's more of a comfort level issue."
Former astronaut Jay Buckey, now at Dartmouth Medical School in Hanover, New
Hampshire, US, says that both temporary and permanent hearing loss were
recorded after flights on the Soviet and Russian Salyut and Mir stations, even
for stays as short as seven days. The lost hearing was usually at higher
frequencies.
The living quarters of the ISS are the Russian Zvezda module, which is the
noisiest module on the station. NASA says the goal is for the working area to
have noise levels at or below 60 decibels (dB) and sleep bunks to be 50dB. At
their peak several years ago, noise levels reached 72 to 78dB in the working
area and 65 dB in the sleep stations. Decibels are measured on a logarithmic
scale, meaning, for example, that 60dB is 10 times louder than 50dB.
NASA has worked to reduce the noise and its effect on the crew. By November
2005, noise levels had been lowered to between 62 to 69dB in the work area and
55 to 60dB in the sleep compartments. Astronauts on the ISS used to have to
wear ear plugs all day but are now only wear them for 2 to 3 hours per work
day.
Intracranial pressure
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According to the US National Institutes of Health, however, noise levels below
80dB are unlikely to lead to hearing loss, even with prolonged exposure.
But while the primary cause of hearing loss in general is high noise levels,
Buckey suggested in a 2001 paper in Aviation Space and Environmental Medicine
that several other factors might contribute to the problem in space.
Elevated intracranial pressure, higher carbon dioxide levels and atmospheric
contaminants may make the inner ear more sensitive to noise, he says. But
there have been no studies yet to test these ideas.
Buckey had designed a device to measure hearing loss of astronauts on the ISS,
but his project was cancelled around the start of 2006 when NASA reduced
funding for life sciences.
NASA has already done much of what it can to reduce noise on the ISS. Crews
have installed fan vibration isolators and mufflers on fan outlets, and
acoustic padding to wall panels.
The current crew, Russian cosmonaut Pavel Vinogradov and US astronaut Jeff
Williams, installed a sound-insulating cover on the Russian carbon dioxide
removal system. They also started adding acoustic padding near the Russian air
conditioner. Future crews will swap out 30 to 40 fans with quieter versions.
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