Whether on stage or listening to your music or films, you should never wear only one in-ear monitor. Also called earphones, in-ear monitors sit within the ear canal and provide the highest caliber isolation of personal audio equipment. Wearing a single earphone increases the risk of ear fatigue and potentially poses a risk to your hearing. This is largely due to a phenomenon called Binaural Loudness Summation, which is a result of how your brain processes sound. When wearing a single in-ear monitor, you’re going to have to turn up your volume to account for the loss of apparent volume and the increase in sound pressure levels can result in unhealthy exposure.
Binaural Loudness Summation
Binaural Loudness Summation (BLS) is a psycho-physical effect where your brain perceives sounds heard by both ears to be louder. This effect is greater with louder sounds, resulting in up to 9dB of apparent loudness at around 90dB of source volume. Anything over 85dB carries the risk of hearing loss if sustained for long enough, so the difference in apparent volume can take you from a safe listening environment to a dangerous one -- especially if you use your in-ear monitors for multple hours a day. Musicians on stage, engineers and audiophiles alike need to be aware of the potential dangers of taking out an earphone.
Musicians are probably at the greatest risk from wearing a single in-ear monitor. In-ear monitors were designed to prevent hearing loss and give performers a higher quality reference while on stage. Used correctly, our monitors excel at this, but used incorrectly, the benefits can all but disappear. However, with all the isolation that in-ear monitors deliver many musicians feel the urge to remove one of their in-ear monitors because they feel disconnected from the audience. This is understandable; performing music is an emotionally driven experience and without the connection to the audience you can find yourself missing half of the feedback necessary to achieve a truly great performance. However, this sensation of being disconnected can be easily circumvented. Place a mic on the audience and add the feed to your mix; not only do you now have control over the volume of the audience, but you’re not going to be disconnected from them. To avoid feeling isolated from your fellow bandmates, your mix is stereo and that you’re panning your bandmates to their relative positions on stage. This will deliver the spacial awareness necessary for the sense of realism, making the band members feel like they’re performing on an amplified stage instead of a silent one. Using these tricks, you can deliver all the information needed for a band to excel while also providing unrivaled control and sound quality.
For audiophiles and music enthusiasts the solution to this problem is to simply be aware that, if wearing a single in-ear monitor, you mustn’t adjust your volume to dangerous levels. If you want the perceived boost from BLS, wear both of your earphones, but otherwise you need to exercise awareness that with a single in-ear monitor in you will not be getting those bonus dBs. The extra loudness from BLS exists only in the mind, but to compensate for not experiencing it, you would need to run your source material louder which can pose a risk to your hearing health.