Abstract
ObjectiveThis 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 prototypes 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 intelligibility during using HPDs was determined based on the speech discrimination score (SDS) at two signal to noise (S/N) ratios (0 and + 5). Data were analyzed using SPSS 22.ResultsThe actual to nominal noise reduction rating values were from 47 to 84% for HPDs. At two S/N ratios, no significant differences were observed in speech intelligibility using HPDs (p > 0.05). At S/N ratio = 0, the speech intelligibility descriptively has been only 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 ratio = 0 (p < 0.05). Increasing the HPDs' noise attenuation values led to an increase in speech interference (p < 0.05). The HPDs with the minimum required noise attenuation while maintaining acceptable speech intelligibility should be worn by employees exposed to medium noise levels.
Highlights
Given that conversation in the work environment is a means of communication, the presence of background noises close to the frequencies of conversation can disrupt communication between employees and even interference with the conversation [1, 2]
At two signal to noise (S/N) ratios, no significant differences were observed in speech intelligibility using hearing protection devices (HPDs) (p > 0.05)
At S/N ratio = 0, the speech intelligibility descriptively has been only improved by using common earmuffs up to 9.07%
Summary
Given that conversation in the work environment is a means of communication, the presence of background noises close to the frequencies of conversation can disrupt communication between employees and even interference with the conversation [1, 2]. The use of hearing protection devices (HPDs) by employees for reducing exposure to background noise can affect their speech intelligibility in the real world. Previous studies showed that the irregular use of HPDs in work environments can be due to lack of comfort, and interference in conversations. Hashimoto et al revealed that a decrease in the noise reduction rates of hearing protectors cannot be considered as a factor for improving speech intelligibility [13]. Fernandes et al showed that at the lowest background noise levels (60 and 70 dBA), HPDs reduced speech intelligibility while the background noise levels were approximately between
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