Great Thread.
Thank you Elizabeth for the Radio Shack sound meter suggestion. I'll buy one tomorrow. FWIW, I copied the table below from the Mayo Clinic Health Information web site. I'm not a Doc, so I can't vouch for it, but something to think about.
Maximum sound-exposure durations
Below are the maximum noise levels on the job to which you should be exposed without hearing protection, and for how long.
Maximum job-noise exposure allowed by law
Sound level, decibels Duration, daily
90 8 hours
92 6 hours
95 4 hours
97 3 hours
100 2 hours
102 1.5 hours
105 1 hour
110 30 minutes
115 15 minutes or less
Source: Department of Labor's Occupational Safety & Health Administration, 2005
But see the following excerpt I pulled off of Wikipedia:
Louder sounds cause damage in a shorter period of time. Estimation of a "safe" duration of exposure is possible using an exchange rate of 3 dB. As 3 dB represents a doubling of intensity of sound, duration of exposure must be cut in half to maintain the same energy dose. For example, the "safe" daily exposure amount at 85 dB A, known as an exposure action value, is 8 hours, while the "safe" exposure at 91 dB(A) is only 2 hours (National Institute for Occupational Safety and Health, 1998). Note that for some people, sound may be damaging at even lower levels than 85 dB A. Exposures to other ototoxins (such as pesticides, some medications including chemotherapy, solvents, etc.) can lead to greater susceptibility to noise damage, as well as causing their own damage. This is called a synergistic interaction.
Some American health and safety agencies (such as OSHA-Occupational Safety and Health Administration and MSHA-Mine Safety and Health Administration), use an exchange rate of 5 dB. While this exchange rate is simpler to use, it drastically underestimates the damage caused by very loud noise. For example, at 115 dB, a 3 dB exchange rate would limit exposure to about half a minute; the 5 dB exchange rate allows 15 minutes.
While OSHA, MSHA, and FRA provide guidelines to limit noise exposure on the job, there is essentially no regulation or enforcement of sound output for recreational sources and environments, such as sports arenas, musical venues, bars, etc. . . .
Many people are unaware of the presence of environmental sound at damaging levels, or of the level at which sound becomes harmful. Common sources of damaging noise levels include car stereos, children's toys, transportation, crowds, lawn and maintenance equipment, power tools, gun use, and even hair dryers. Noise damage is cumulative; all sources of damage must be considered to assess risk. If one is exposed to loud sound (including music) at high levels or for extended durations (85 dB A or greater), then hearing impairment will occur. Sound levels increase with proximity; as the source is brought closer to the ear, the sound level increases.
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The bottom line, if there is one, is that 90 db may be too high. The same may be true even at 85db. It could very well be that Elizabeth's 77db guideline is conservative and the safest of all. Of course, time exposure is important too. If there are any audiologists or ENT Docs out there, please weigh in. This is a very important topic.
