Speech discrimination and effectiveness of hearing aids under listening conditions similar to those of a transit operator.

Some controversy exists regarding regulations that permit hearing impaired drivers to operate passenger carrying vehicles. In other situations it has been shown that the hearing impaired generally have more difficulty than normals discriminating speech in noise. The present study investigates this under listening conditions simulating those of a transit operator, and also looks at the effects of a hearing aid on speech discrimination in the same situation. One normal hearing group and three groups representing varying degrees of symmetrical sensorineural hearing loss were given a sentence type discrimination test in a background of recorded diesel bus noise at different speech-to-noise ratios. The hearing impaired groups performed more poorly than normals and the use of hearing aids did not affect the performance of the hearing impaired groups. Regulations pertaining to licensing of transit operators should take into account hearing above 2,000 Hz. The results of this study, combined with the possibility of noise damage from amplified noise levels, lead us to conclude that hearing aids should not be worn by transit operators on the job.