For the vast majority of musicians a hearing protector that provides a flat or uniform attenuation is the way to go. A hearing protector with a flat attenuation means that the lower frequency fundamental and higher frequency harmonics are all treated the same- everything is attenuated by the same amount that ostensibly reduces the sound level of the music from a damaging to a non-damaging level. In the case of the ER-15 musician earplug, this 15-dB uniform reduction means that the wearer can be exposed 32 times as long as without hearing protection.
For those who like math, every 3-dB decrease cuts in half the potential damage … so a second 3-dB reduction brings it down to ¼ of the original potential damage, and another 3 dB (now we are at 9 dB of attenuation) brings the damage down to 1/8, another 3 dB brings it down to 1/16, and finally another 3 dB (15 dB of attenuation) takes us down to 1/32 of the potential damage. Unfortunately for those who don’t like math, it’s still the same thing.
But what about those musicians who require a little protection from some percussive high-frequency sounds? What about the clarinet player who sits or stands in front of the percussionist and cymbal? This is where a vented/tuned earplug can be useful.
As the name suggests (I actually named it so all blame for the name should be aimed at me), a vented/tuned earplug has a select-a-vent and bore drilled down the center. In its most open (3-mm condition) the earplug is essentially acoustically transparent up to about 1000 Hz, with an attenuation in the higher frequencies above this point. In its most occluded (SAV complete cover) the earplug is like any other occluding custom earplug.
Returning to its most open condition, this earplug can be quite useful when I attempt to play my clarinet while the percussionist is whaling away behind me. Most of the energy of a percussive sound is mid- to high frequency. This is certainly empirical but also derives from simple acoustics. Any sudden increase in pressure (over a short time period) such as a percussive rim shot, has a short wavelength, which means it has high-frequency energy. Again, for those who like math, this sudden increase in pressure over a short period of time can be thought as ¼ of the entire wavelength, so 4 times this amount is a full wavelength, and this time period is still quite short… or high frequency.
In its most open condition, the vented/tuned earplug will allow all of the sound of the band or orchestra through (including most of the sound energy of one’s own instrument), except it will provide attenuation from the abrasive higher frequency sounds.
The vented/tuned earplug is not for everyone or for all conditions. If someone is playing in a relatively quiet environment that may include jazz or soft rock, it would be useful. It would have limited utility for rock and full orchestral sounds.
But all is not as it seems! Well, it actually is but I just wanted to sound mysterious. All vents have a “vent-associated resonance.” This is the same whether it’s true of hearing protectors or true of hearing aids with vents. This resonance is created by the mass of air in the vent oscillating at about 400-500 Hz. For those who like math, it is called an inertance, and of course, it’s still called an inertance even if you don’t like math. Most audiology textbooks refer to it simply as “mass,” but that is only an acoustic analogy; audiologists call this “mass” and engineers call it an “inertance” but it’s the same thing.
This 400-500 Hz resonance can actually be helpful, especially for vocalists. How often have we seen singers who intentionally block one ear when they sing? This creates the occlusion effect, which, because of the low-frequency enhancement, helps singers to hear themselves better. While it’s not the same thing, this mass-associated resonance enhances sounds in the 400-500 Hz region- not as broad bandwidth as the occlusion effect (all sounds less than 1000 Hz) but at least there is an enhancement from 400-500 Hz.
The vented/tuned earplug is not for everyone, but for vocalists, and those who play relatively quiet musical instruments (such as the clarinet) but are in environments with significant higher frequency (percussive) sound, the earplug may be a handy alternative.
As an experiment, if one of your clients is using the ER-15 musician earplugs, have him take out the attenuator button; what is left is not too much different from a vented/tuned earplug in its most open condition.