Thanks for this thread. I worked in a power plant for 21 years, and exposure to extremely loud sound happened every day. I always ran around with a huge pocket of the best earplugs, but unexpected noise happened. Before I left for good, my plant was experiencing 1 - 2 EXTERNAL tube leaks a month. At over 1000psi and 480 - 510 degrees Fahrenheit, it was a miracle no one was ever killed. I don't need to bore anyone with more details. Suffice to say a steam plant isn't hearing-friendly. I should have been a librarian! The constant whistling tone in my head is very tough to get used to.