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  • Tom Trones

Custom Molded Earplugs - The Myths and Truths

Updated: Feb 26


At the turn of the century, I was in a band with 3 young hopeful metal heads rocking up a storm in my friend’s tiny basement. It was LOUD. Our drummer’s powerful strikes meant having to change broken cymbals and drum heads on a monthly basis. My “puny” 80-Watt guitar amplifier was struggling to keep up, so I pointed it straight into my ears, about a foot away. It was even LOUDER, but at least I could hear myself.


Fortunately, I had the foresight to wear hearing protection. Cheap foam earplugs were not working out, muddying the listening experience by removing so much of the high frequencies. So, I took the leap and got custom molded musician's earplugs. A leap from 0.2$ to 250$ in today’s value was a hefty investment for a 17-year old.  I invested in my hearing, and I am glad I did, as I ended up with a career using my ears as my primary sense. Custom molded musician’s earplugs are almost always portrayed as an be-all and end-all of hearing protection, however there are definite downsides. If you are buying into the uncomfortable, potentially painful and time-consuming molding process, you want to have realistic expectations to what you are getting.


Myth #1: Custom molded earplugs must fit perfectly, as they are made specifically for your anatomy.

·     Singing, chewing or any movement of the jaw often introduces leaks and thereby audible and annoying changes of the sound (foam is better here)

·     Even newly molded earplugs can have bass (low frequency) leaks, decreasing the protection and perceived flatness

·     Ear canal anatomy changes with age and is quite sensitive to weight fluctuations, thereby compromising fit/leaks/sound quality



·     Most can achieve equal or better fit with universal tips (foam or silicone), except for the few percent with oddly shaped ear anatomy

Truth: There are real issues related to getting a perfect fit with custom molded earplugs.


Myth #2: Custom molded earplugs must be super comfortable.

·     For many people they are more uncomfortable to wear over long periods compared to foam tips due to sweat and material hardness

·     They are manufactured slightly larger than your ear canal to try to avoid leaks, but this pressure is uncomfortable over time

·     If not specifically made for sleeping, the material hardness makes them uncomfortable for sleep


Truth: There are real issues related to comfort with custom molded earplugs.

Real advantages of custom molded earplugs

·     Available membrane-based filters with high quality sound (also true for universal fit)

·     Increased choice of colors and materials the last years improve on the usually quite medical aesthetic, and can potentially be relatively visually discreet

·     Easier to insert quickly and with one hand compared to foam tips, although they can be hard to grab and remove

·     The molds (with filters removed) are non-porous and relatively easy to clean 

Custom molded musician’s earplugs are for now the best overall option out there if you want natural sound. However, we at Minuendo are soon releasing a product that will address many of the downsides of existing earplugs and finally introduce innovation to a product segment that has been largely dormant for decades. Seeing many of my fellow musician friends struggle with tinnitus and premature hearing loss is a true motivation to create better products for them as well as new generations of basement rockers.

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Technical afterword

Musician’s or lossless earplugs classify products that go to great lengths to keep the perceived frequency response flat and natural sounding. Filters vary in sound quality across the attenuation ranges, where filters around 15dB are generally the flattest. Typically, the membrane filters are made by manufacturers like ACS and Etymotic while the custom molds are made by local establishments. Note that professionally made molded earplugs are referenced in this article, not the more unreliable DIY types.

The fit-uncertainty of custom molded hearing protection is thoroughly scientifically established and well known in the literature, although heavily under-communicated to consumers. Attenuation uncertainty is the main driver for current changes in ANSI/ISO standards for measurement and certification of Hearing Protection Devices. In the following figure, attenuation uncertainty is shown for custom and non-custom earplugs without membrane filters, for users trained and untrained in insertion. They are largely comparable, although custom earplugs do generally have a less uncertainty than non-custom. However, non-custom earplugs have an advantage in creating a tighter seal at bass frequencies, which is important to achieve a flat frequency response when a membrane-based filter is inserted. Tufts et al. (2012) shows that custom molded earplugs have a quite high standard deviation of 6,4 dB at 250Hz for untrained users.


Kvaløy et al. (2010) found that deeply inserted foam has a higher attenuation on all frequencies and that the mean and standard deviation of the attenuation (trained user with fit test) is as good as for an optimally fitted custom silicone earplug.

Sources:

Tufts, Jennifer & Jahn, Kelly & P Byram, John. (2012). Consistency of Attenuation across Multiple Fittings of Custom and Non-custom Earplugs. The Annals of occupational hygiene. 57. 10.1093/annhyg/mes096.

Kvaløy, Olav & Berg, Tone & Henriksen, Viggo. (2010). A Comparison Study of Foam versus Custom Silicone Earplugs Used as Part of an Intelligent Electronic Hearing Protector System. International Journal of Acoustics and Vibrations. 15. 151-155. 10.20855/ijav.2010.15.4267.

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