Noise on the International Space Station (ISS) is the most serious issue about living in space, according to ISS crews. They say they are forced to wear ear plugs and headsets due to the continuous noise, largely attributed to cooling and circulation fans. Most noise comes from the Russian Zvezda service module, but the US Destiny laboratory is also noisy. To meet the ISS schedule, two Russian modules were accepted for flight despite not meeting safety limits for noise.
Source: Flight International