Question
Is there data on the amount of attenuation/NRR for custom silicone and acrylic earmolds as noise protectors? How do they compare with foam and premolded flanged disposables that are typically used?
Answer
Yes, there is detailed attenuation data available for custom fit Hearing Protection Devices (HPDs) available from Westone. This information lists Noise Reduction Rating (NRR) test results and the average attenuation per frequency for these custom earpieces. Our NRR test results are available on our website (https://www.westonelabs.com) or by calling one of our customer service representatives at 1-800-525-5071.
The answer to the second part of your question is a bit more complicated. The test results can vary depending on when the NRR testing was done, as the NRR protocol has changed over time. It used to be that a manufacturer's representative was allowed to participate in the fitting of earplugs (on the test subjects) prior to the test subject entering the test booth. The generic fit plugs were often inserted deeply and carefully (by someone other than the actual test subject). Needless to say the test results for generic fit products tested under these conditions was fantastic. Given that situation, there was no debate as to whether the test subject was wearing the earpiece properly and very high NRR results were obtained. However, results in the ''real world'' workplace environments were not as satisfactory.
To function properly and achieve the same NRR results as those achieved during previous testing, most of the generic products required practiced manipulation and deep insertion of the hearing protector in the ear. This manipulation was, and still is, quite difficult for some people to master and the insertion depth required can be quite uncomfortable for many users.
A study undertaken in the late 1980's confirmed that most users of generic foam earplugs with an advertised NRR of 29 to 31 dB were actually only getting 11 dB of hearing protection in the field. When worn properly, as was confirmed by the NRR testing, generic products are quite capable of producing impressive results. In the field, however, the results are not as impressive.
Custom made hearing protection bypasses most of the issues associated with generic earpieces. Custom made products are fit to the wearer's ears, thereby taking advantage of specific anatomical features to ensure consistent, repeatable and comfortable results. Thus, the results in a controlled test environment are very consistent with actual field use, unlike many generic fit products. Custom made wins out on all fronts, except price. However, price objections can be negated when the cost is amortized over the life of the custom made earplugs as compared to the ongoing cost of disposables.
BIO:
Westone Laboratories, with full service facilities in Colorado Springs, Seattle, and Kalamazoo, Michigan, is the industry leader in the creation and manufacture of custom earmolds and hearing protection, as well as clinical supplies and products for the end user. Started by the Morgan family in 1959, Westone has produced over 7 million earmolds, each one custom-made. Randy Morgan, President & CEO, called upon his core team to assist in addressing this question. With over 200 years combined experience, the team consists of staff audiologists, lab managers, research engineers and earmold technical experts.