See Noise Exposure of Music Teachers for important information on this article.
The only way to be sure is to have it tested, but here are a few warning signs:
All of these situations offer direct but informal comparisons between your hearing and that of the people around you. Isolated incidents are not significant but a pattern may be telling you something.
Consonants are shorter than vowels and are the first to be lost.
You may have a habit of helping your hearing with a bit of subconscious lip-reading. If so, it has probably developed so slowly that you didn't notice.
This kind of sound is called 'tinnitus.' Tinnitus is not a direct symptom of hearing loss but is often associated with it. Short-term tinnitus, e.g. after a loud concert, is a response to short-term over-exposure and repeated short-term over-exposure leads to hearing loss. Chronic tinnitus is often associated with long-term hearing loss. If it is at a very low level, it will only be heard in very quiet surroundings.
You may be hearing your own tinnitus; see above.
This may seem odd but it is in fact quite typical of people with hearing loss. The phenomenon is known as 'recruitment.'
None of these symptoms are necessarily signs of immediate or severe problems. As I said in the introductory article, Noise Exposure of Music Teachers, this information is correct to the best of my understanding but is not definitive, so don't panic and do seek more information if you have concerns.
The Health & Safety Executive [UK] website (general) and the articles by Chasin (general but with specific reference to music and musicians) and Newman (tinnitus) shown in Noise Exposure of Music Teachers: Links are good starting points for further reading but ultimately the only way to be sure of the state of your hearing is to visit an audiometrist or audiologist to have it tested.
Malcolm Tattersall. Last amended 16 February 2006. Entered on Knowledge Base 22 April 2014. Minor amendments requested by author entered 1 May 2014.