The Effect of Hearing Protection Devices on Speech Intelligibility of Persian Employees

Abstract

Objective This study aimed to investigate the effect of hearing protection devices (HPDs) on speech intelligibility in Persian work environments. Three current earmuffs and three earplugs and one of the prototype of molded earplug were tested on 15 male subjects which were randomly selected. The noise reduction of HPDs was measured based on the Real Ear attenuation at Threshold (REAT) method. Speech intelligibilities during using HPDs were determined based on the speech discrimination score (SDS). Data were analyzed using SPSS, version 22. Results The actual to nominal noise reduction rating values were from 47–84% for HPDs. The earmuffs show higher ratios of actual to nominal noise reduction compared with the earplugs. At two signal to noise ratios, no significant differences were observed in in speech intelligibility using HPDs (p > 0.05). However, at S/N = 0, the speech intelligibility descriptively has been improved by using common earmuffs up to 9.07%. There was a significant difference up to 21.27% in speech intelligibility for proposed molded earplugs at S/N = 0(p < 0.05). It is concluded that, if the trend of signal to noise ratio is positive, the HPDs will reduce the ability to understand speech.