Date of Award
Doctor of Audiology (AuD)
School of Communication
Using a PLD in an automobile introduces unique threats such as volume levels set at higher levels to reduce the masking effects of road noise that enters the automobile. Passengers enjoying prolonged PLD exposure may be at an increased risk of noise exposure or fluctuating sound pressure levels resulting in hearing loss. Historically, hazardous noise has been primarily associated with industrial/occupational activities; however, harmful noise from recreational activities is also prevalent. The Center for Disease Control (2015) lists turning down PLD volume as one of their top three methods for reducing the possibility of NIHL in children. Excessive listening level and prolonged duration of use put listeners at risk for increased thresholds and other repercussions of hearing damage.
The combined effect of simulated road noise and PLD volume was measured in a simulated ear canal. The principal investigator collected all sound levels using KEMAR; no human participants. A pre-selected movie scene was delivered to KEMAR at normal listening levels through earbuds and headphones separately, while in the presence of road noise. The movie scene and road noise were increased in 5 dB steps and recorded.
The results showed earbuds are better designed for eliminating the masking effects of road noise, yet headphones are better designed for limiting the maximum SPLs. Frequent volume changes as high as 41 dB were reported in this study.
Himstedt, Hayley, "" (2017). Dissertation. 70.