Extensive training has been shown to improve the effectiveness of hearing protection devices (HPDs) in reducing noise exposure for workers. This study aimed to (1) assess the evidence for short- and long-term effectiveness of HPD fit testing paired with extensive instructions and (2) identify the type and frequency of refresher instruction associated with maintaining its effectiveness. A literature search was completed on February 5, 2025. The inclusion criteria focused on uncontrolled before-and-after (UBA) studies that reported personal attenuation ratings (PARs) provided by HPDs in the field. A total of 23 UBA studies involving 5,575 workers were included, meta-analyses were performed when multiple comparable studies were located. For earplugs, retesting immediately after extensive training increased the mean PAR by 12.88 dB (13 studies) compared with the pre-intervention PARs without instructions. The improvement decreased to 8.84 dB (2 studies) within 6 months and further reduced to 4.46 dB (2 studies) at 12 months. For earmuffs, only one study reported increase in PARs of 5, 2, and 3 dB for immediate, short-term, and long-term assessment, respectively. Introducing extensive refresher training within a 6-month interval increased the mean PAR from earplugs by 1.53 dB (2 studies) compared with the post-intervention PAR retested immediately after extensive training, with a further increase of 3.45 dB (1 study) following annual extensive instruction. Simple refresher instructions within a 6-month interval maintained the PAR values (1 study). However, without any refresher training, the PAR decreased by 2.64 dB (2 studies) within 6 months and 3.09 dB (2 studies) over 6 months or longer. Refresher training may increase the probability that workers receive efficient protection from their HPDs. However, more high-quality studies could help inform the optimal type and frequency of refresher training.
Gong et al. (Tue,) studied this question.
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