Hearing protectors and speech perception
Reviewed by Richard Navarro

This study tested 31 subjects using hearing protectors by maintaining a constant intensity level for the speech signal while varying background noise levels. The goal was to use this test to detect speech perceptual abilities under different hearing protectors – passive vs. electronic filtering. The results showed that electronic filtering resulted in the best overall speech intelligibility. The study elucidated the various types of noise that may be encountered in workplace situations and discussed the implications of the different noises for differentiating between hearing protectors. There are many variables in trying to conduct such a study and deriving meaningful conclusions. One potential caveat is that most speakers will automatically elevate their vocal effort in noise (Lombard effect) to speak over the noise. This reduces some of the power of the study’s conclusion that the proposed test is a viable method for differentiating hearing protectors. 

To measure the impact of hearing protectors on the perception of speech in noise.
Hiselisu P, Edvall N, Reimers E.
INTERNATIONAL JOURNAL OF AUDIOLOGY
2015:54:S3-S8.