We work in a humid environment and use moisture-absorbing pads with our earmuffs. Do the absorbent pads affect the attenuation of the earmuff?
Earmuff users know that anything interfering with a good seal around the ear (thick hair and eyeglass frames or large earrings) can potentially compromise the attenuation of the earmuff. Workers who wear the absorbent pads, such as the Howard Leight Cool Pads, may likewise wonder if their earmuff attenuation is being compromised. Cool Pads come with an adhesive backing that attaches directly to the earmuff cushion. As an option, the punched oval center of the Cool Pad may also be placed inside the earcup to protect the foam filling of the earmuff. These are ideal for humid and moist environments, for users who perspire heavily or for settings where the same earmuff is shared among multiple users.
In a study conducted at the Howard Leight Acoustical Laboratory, Cool Pads were tested with a representative earmuff (Howard Leight Thunder® T2). Hearing tests were administered to listeners while they wore the earmuff alone, and then with the pad attached, to determine any change in earmuff attenuation.
The results in Table 1 show that the addition of the Cool Pad causes a mild drop in attenuation of about 2.5 dB in the low frequency response (500 Hz and below) of the earmuff, but no significant difference above 500 Hz. The addition of the punched oval center into the earcup actually increases attenuation in the earcup by about 1 – 2 dB in the high frequencies (4000 Hz and above).
If we apply these results to the Noise Reduction Rating (NRR), the addition of the Cool Pads would decrease the NRR of an earmuff by 1 dB or less. Using the Cool II with the punched oval center pad in the earcup would decrease the NRR by about .5 dB. These minor changes in overall attenuation (1 dB or less) are within the standard deviation of the testing, and will likely be unnoticeable and insignificant to most users when compared with the benefits of extra comfort, longer wear time and additional hygiene provided by the Cool Pads.