This is an important topic, especially for percussionists, and comes up regularly.
Tinnitus and hearing loss can both be caused by loud percussive sounds and can both become permanent conditions. They are cumulative and generally get worse with months or years of repeated exposure to loud sounds. Available treatments are not satisfactory, and generally do not return you to your previous state with no hearing loss or tinnitus. At first, both conditions are temporary and generally go away hours after the loud noise. With repeated exposure to loud sounds, they last longer and longer and then become permanent. So prevention is the key, which generally involves avoiding loud sounds (get the others in your group to play softer) or using hearing protectors.
Some of this, and some reasons we should all consider using hearing protection in appropriate settings, have already been discussed in the Tinnitus thread.
viewtopic.php?f=5&t=4357&hilit=tinnitusThe question was raised today about soft foam vs custom molded vs commercial flat response hearing protectors (eg, Etymotic ER-20) for playing music. The ideal hearing protector for playing music would cut all frequencies equally, ie would be "flat" across the audible spectrum. Hearos and other foam earplugs effectively reduce volume, but cut the high frequencies relatively much more than the low frequencies. This makes the music sound muffled and distorted. If you are just worried about hanging out in a club with "DJ Sordo", the foam earplugs work fine. But for playing music when you need to be in key and in time with the other musicians, there are much better options. All available hearing protectors greatly reduce frequencies above 8,000 Hz, but some specially designed hearing protectors are relatively "flat" in their loudness reduction at frequencies below that. Many of the high pitched percussive sounds we need to cue our timing, such as bell, kata, timbale cascara, bongo martillo, guiro, claves, or maracas fall in the 1,000 to 8,000 Hz range. Both foam and specially designed hearing protectors reduce sounds about 20 dB at all frequencies below 1,000 Hz, but foam earplugs reduce the important high frequency sounds much more than the lower frequencies. For example, at 4,000 Hz, the loudness is still reduced about 20 dB with the ER-20s but about 33 dB with the foam ear plugs. A 13 dB cut in loudness is perceived as reducing loudness by more than half. That 13 dB additional cut in the high frequencies relative to the lower frequencies makes the high pitched percussive instruments much harder to hear over the other instruments, the vocals, and all the reflected sounds onstage. So it is easier to play with other instruments using the ER-20s than with the foam earplugs.
Here is a graph from the Etymotic Research website showing the difference between the ER-20s and foam earplugs.
http://www.etymotic.com/ephp/er20-ts.aspxBy the way, I have no connection with Etymotic Research and no interest in pushing the ER-20 hearing protectors specifically. I am an end user, but I have not found any other brand of hearing protector that works as well for playing music. Also, they have a very informative website which is good for illustration.
The custom molded hearing protectors that use ER-9 or ER-15 inserts (also made by Etymotic Research) do work better than the ER-20s in my experience. I usually do best with the ER-9 that reduces the loudness by about 9 dB, 20 dB is not necessary in most clubs or rumbas. Unfortunately, the molding process and custom fitting increase the cost from about $12 for the ER-20s to $200-$300 for the custom molded hearing protectors. But new ears are priceless (and unavailable with current medical technology). For most loud clubs and bands, and musicians with normal hearing, the ER-20s work well enough.
Here is a graph of the difference between the ER-9, ER-15, and ER-25 inserts for the custom molded hearing protectors. The ER-15 is the flattest response, much flatter than the ER-20.
http://www.etymotic.com/ephp/erme-ts.aspx