Astronauts returning from extended stays at the International Space Station (ISS) have been reporting high frequency hearing loss. The cause of the hearing loss is unknown, because noise levels are between 62 to 69dB in the work area and 55 to 60dB in the sleep compartments. Hearing loss should only start at 80dB. At one time, the ISS had sound levels at up to 78dB, but that number has since been drastically reduced (keep in mind the Decibel scale is logarithmic, which means that 50dB is ten times louder than 40dB). Astronauts on the station are now only required to wear earplugs for 2-3 hours a day, whereas at 78dB, the earplugs were required constantly.

One explanation for the hearing loss has been elevated intracranial pressure, higher carbon dioxide levels and atmospheric contaminants that make the inner ear much more sensitive. Unfortunately, no tests can be made at this time as NASA has no funding for the project. Hopefully in the future this will lead to a solution, but for now the current crew is taking steps to insure their own hearing. They have placed sound insulating materials and padding on the air conditioning unit. Plans are in place to swap 30-40 noisy fans with quieter ones.

Loud machinery might seem like a minor problem, unfortunately though for those staying at the ISS, this minor problem can have major consequences.