Question
A nurse at a local hospital has called our office seeking information about hearing conservation guidelines for neonatal babies being air transported. They use small sound meters in the incubators that are reading high levels of about 95-97dB. She has been using small foam plugs, cut and tapered to protect the hearing of the neonates, but wonders what is the correct procedure. Do you have any guidance as to whom to contact or any info on this?
Answer
There are actually two questions here. First, are the levels cited high enough to cause concern? Second, if noise protection is pursued, what is the best approach? The decibel levels cited were given without a weighting scale. When taking sound level measures, the A-weighting scale is typically used because it is the most similar to the response of the adult human ear. We do not have regulations or guidelines specific for neonates. Furthermore, we don't know if they are more susceptible to noise induced hearing loss than adults. If we use the adult regulations, the Occupational Safety and Health Administration specifies that measures be made with the A scale and a slow response time. For 95 dBA up to 4 hours of exposure would be permissible. For 96 dBA up to 3 hours would be permissible. Aside from noise exposure, high noise levels can be physiological stressors (e.g., increased heartrate) and this is another reason to try to provide noise protection.
If you decide to provide noise protection to decrease the likelihood of noise induced hearing loss or for promoting a good environment for physiologic reasons, I would suggest that you use over-the-ear coverage rather than inserting a plug into the ear. Neonates often have debris in the canal due to the birth process. This usually will naturally migrate out over a period of days or weeks. Without an otoscopic inspection, you do not know whether you are pushing debris and/or cerumen further into the canal. This could make the debris less likely to migrate out naturally. By using a muff that covers the pinnae, you avoid this problem. Although I do not endorse a specific manufacturer, Natus makes a product called Minimuffs that reduces sound levels by at least 7 dB. It fits over the outer ear and stays in place with a hydrogel adhesive.
www.osha.gov/pls/oshaweb (see Table G-16)
www.natus.com/products/minimuffs.html
ROANNE KARZON
Roanne Karzon received her Ph.D. from Washington University. Currently, she is a clinical assistant professor of Audiology at the Central Institute for the Deaf and a clinical assistant professor, Dept. of Otolaryngology, at Washington School of Medicine.