## 4 Discussion  
This study exclusively involved noise-exposed mill workers who were required to be fully compliant with the use of HPD at all times during their working hours. However, our findings showed that the average baseline HPD usage among the participants was only in the region of 60%. Considering the risk of hearing damage in such a population of workers, the level of compliance was alarmingly low, albeit higher than in the findings reported in another local study among manufacturing workers, in which the average self-reported HPD use was only 38% [5]. In a survey conducted among industrial workers in Thailand, the average HPD use was higher, at 78% [15]. Another study on HPD use in America also reported relatively high baseline HPD usage, ranging between 75% and 79% [13]. Our targeted training module was shown to effectively improve the percentage of HPD use among workers in the intervention group. There was a significant increment of 10.3% from the baseline HPD use of 66.7%. This result differs from the findings reported in a study among factory workers in America, which showed no significant change in HPD use after 6 months among those who received targeted intervention and control intervention [13]. In a study involving construction workers in America, a targeted training module increased the use of HPD by 6.1% in twelve months. The same study also reported an increment of 8.3% among workers who received tailored intervention. However, the author suggested that targeted intervention provided better value when compared to tailored intervention as it was cheaper and less time-consuming [12]. The targeted intervention in our study also increased the intention to use HPD from 77.3% to 89.3%. This trend can be seen as an indication of a better level of compliance in the future. A probable reason behind the effectiveness of the targeted module as compared to the standard module was the shorter duration of the training session. The one-hour session for the intervention group was adequate to disseminate all the main points while being  
Figure 2: HPD use and intention to use HPD over time. concise enough to maintain the participants' attention. Although there is no conclusive evidence to determine the typical attention span of an adult, we felt that a session exceeding an hour would leave the participants feeling fatigued and unable to concentrate on the presentation [18]. Another factor that may have contributed to the change in the participant's behaviour was the utilisation of actual audiogram results as a component of the training session. We believe that the interactive session in which workers were asked to interpret their annual audiograms significantly increased the level of awareness regarding susceptibility to hearing damage and effectively improved compliance with HPD usage in the intervention group. The positive effect of informing workers about their audiogram results on the intention to use HPD was previously suggested in another study involving construction workers [14]. Despite having accomplished our target to improve the use of HPD, the mean percentage for the intervention group only reached 77% at follow-up, which is far less than the desired 100%. Based on the participants' questionnaire responses, the main barriers to compliance were the lack of comfort and communication difficulties. Their responses were consistent with the findings of a qualitative study on HPD use among local sawmill workers. The study identified three main themes related to HPD use, namely lack of comfort, lack of awareness, and communication barriers [19]. Interestingly, another qualitative study in New Zealand on the same topic also highlighted, among others, feeling uncomfortable and communication problems as factors that hindered workers' use of HPD [20]. Notwithstanding the fact that knowledge and awareness regarding noise hazards are essential to promote HPD usage, the provision of training alone may not be adequate to address the abovementioned issues.