Measuring earplug noise attenuation: A comparison of laboratory and field methods

Figures & data

Table 1. Tested earplugs.

Earplug	Descriptor	Type	Size	Impression Technique	NRR	n
EP1	Roll-Down Slow Recovery Foam	Non-Custom, Disposable Foam	Universal	NA	29	42
EP2	Roll-Down PVC Foam	Non-Custom, Disposable Foam	Universal	NA	29	46
EP3	Push-to-Fit Foam with Cord	Non-Custom, Hybrid	Universal	NA	32	43
EP4	Polymer Quad Flange with Cord	Non-Custom, Premolded	Universal	NA	27	49
EP5	Full Shell Solid Silicone with Cord	Custom	Custom	Physical	29	44
EP6	Full Shell Solid Silicone with Cord	Custom	Custom	3D Scan of Physical	29	48
EP7*	Canal Silicone Rubber with Cord	Custom	Custom	3D Scan of Ear Canal	26	37

Note: *This earplug is no longer commercially available. EP = earplug, NRR = noise reduction rating, n = sample size for tested product.

Figure 1. Mean group attenuation (in dB) by test system. Note. Sample size (n) differed by test-by-test system (REAT n = 57, FCS n = 57, CCF-200 PT n = 30, CCF-200 NBN n = 27). error bars are ± 1 SD. ^‡ significant difference between the REAT and the FCS, the REAT and CCF-200 PT, and the REAT and CCF-200 NBN at p < .0001. REAT = Real ear attenuation at threshold, FCS = FitCheck Solo, PT = pure tone, NBN = narrowband noise, dB = decibel.

Table 2. Average difference in attenuation (in dB) from NRR by earplug type.

Earplug Type	n	Mean	SD
Non-Custom	55	1.5*	5.3
Custom	51	−3.8^‡	4.5

Note. Reported attenuation values were obtained with the REAT test system. *Significant at p < .05, ^‡significant at p < .0001; Non-custom Group includes EP1, EP2, EP3, and EP4; Custom group includes EP5, EP6, and EP7. N = sample size, SD = standard deviation.

Figure 2. Measured REAT attenuation (in dB) by earplug. Note. Sample size (n) differed by tested earplug. The solid horizontal line is the manufacturer-provided noise reduction rating (NRR) for the tested earplug. ^‡significant at p < .05, *significant at p < .0001. The tested earplug (EP) types were EP1 = disposable foam, EP2 = disposable foam, EP3 = hybrid push-to-fit foam with cord, EP4 = premolded quad flange with cord, EP5 = custom full shell with cord manufactured from a physical impression of the outer ears, EP6 = custom full shell with cord manufactured from a 3D scan of the physical impression, and EP7 = custom canal with cord manufactured from a 3D scan of the ear canals.

Data availability statement

The datasets generated during and/or analyzed during the current study are not publicly available due to government restrictions regarding data sharing but are available from the corresponding author on reasonable request and when requirements are met.