Over the past decade, the increased market penetration of in-ear monitors for stage monitor use has been dramatic. For live sound engineers, the benefits have been myriad: lower overall stage volumes, less wash from the stage to interfere with the signals the audience hears, faster setup time and less weight on the truck. FOH engineers are freer to mix their mix aesthetically, not in combat mode with the sound emanating from the stage. Lower stage volumes can mean lowered volumes for the audience and greater fidelity and intelligibility; these benefits have been especially lauded in houses of worship and small-room sound reinforcement. These are all real and concrete motivators driving the in-ear monitor movement.
One aspect of in-ear monitor marketing deserves further inspection: The devices have been touted as providing musicians (and monitor engineers) some degree of hearing protection. While lowered stage volume levels are a step in this direction, actual listening levels actively chosen by musicians (after all, they now have direct control of the volume knob) may prevent this potential benefit from being realized.
A few years back, Vanderbilt University researchers worked with performing musicians, studying both their preferred and minimum acceptable listening levels for their own voice when using both stage monitors and in-ear monitors, measured in-ear, with a background of a variety of instrumentation. The study found that, on average, preferred listening levels selected by musicians were only -0.6 dB SPL when using in-ears as opposed to stage monitors, a level difference deemed significant, even if marginal for protecting hearing. When musicians were worked with and educated, trained to dial in their minimum acceptable listening levels rather than their preferred listening levels, inear monitors were clearly superior in their potential for hearing protection, allowing reductions of 6 dB on average when using in-ear monitors as opposed to traditional stage monitor loudspeakers.
Inspired by their own research, in-ear monitor maker Sensaphonics developed a device called dB Check that allows users to monitor their own listening levels. The device is placed inline between the monitor driver and the in-ears, using a voltage measurement and the known sensitivity of Sensaphonics’ and other select drivers to calculate the SPLs in ear. dB Check is the only practical device I know of that allows a musician self-calibration, even comparing cumulative listening volumes to established standards for hearing protection. This is a huge step forward in an individual’s ability to monitor his/her own behavior.
The ultimate point here is that musicians and engineers should not assume that using in-ear monitoring in and of itself provides hearing protection. Safe practices are literally in their own control, as close as the volume knob for their in-ear monitor amplifier.