In-ear monitor (IEM) systems can assist in preventing hearing damage, but they aren't foolproof protection. Although there's no direct correlation between where to set your volume control and how much SPL is present in your ears, here are a few suggestions to help protect your hearing.
1. Use an isolating earphone. Desired sounds must be at least 6 dB louder than any ambient noise. Average live music levels typically run 110 dB SPL, where hearing damage can occur in as little as 30 minutes. To hear IEMs when using a non-isolating earphone would require a sound level of 116 dB SPL, which can be dangerous. Inexpensive “ear buds” offer little, if any, isolation. Avoid these types of earphones for personal monitor applications.
2. Use both earphones. Using only one earphone is equivalent to using a non-isolating pair of earphones, except that one ear will suffer damage twice as fast as the other one.
3. Keep the limiter on. Unexpected sounds, such as those caused by someone unplugging a phantom-powered microphone or a blast of RF noise, can cause a personal monitor system to produce instantaneous peaks in excess of 130 dB SPL. A brick-wall type limiter can effectively prevent these bursts from reaching damaging levels. Only use a personal monitor system that has a limiter at the receiver, and don't defeat it for any reason.
4. Pay attention to what your ears are telling you. Temporary Threshold Shift (TTS) is characterized by a “stuffiness,” or compressed feeling, like someone stuck cotton in your ears. Ringing (or “tinnitus”) is another symptom of TTS, which is the ear's way of telling you that you're being exposed to sound levels that are too extreme. The effects of TTS are cumulative, so if you regularly experience these effects, your monitoring level is too loud and hearing damage will occur with repeated exposure to those levels. Turn it down!
5. Have your hearing checked regularly. The only certain way to know if your listening habits are safe is to have your hearing checked regularly. The first hearing test establishes a baseline that all future hearing exams are compared against to determine if any loss has occurred. Most audiologists recommend that musicians have their hearing checked at least once a year. If hearing loss is caught early, corrections can be made to prevent further damage.
Personal monitors can go a long way toward saving your hearing, but only when used properly. Monitoring at lower levels is the key to effective hearing conservation, and this can only be accomplished through adequate isolation. Used correctly, professional isolating earphones, combined with the consultation of an audiologist, offer the best possible solution for musicians interested in protecting their most valuable asset.
The table above shows OSHA and EE (Equal Energy) recommendations for exposure time versus sound pressure level.
Sources: Shure Incorporated, Sensaphonic