Table 2 Characteristics of Interventions and Major Findings

Reed et al. (2001) [37]

1) Narrative simulations based on stories on farm activities and 2) Simulations of farm tasks while students pretended to have a disability

AgDARE curriculum improved safety attitude and behavior

 • Long-term impact on hearing protection use was examined only in small a subset of adolescents.

 • Control group was older than the intervention groups.

 • Not a clinical trial.

 • Only safety attitude changes were measured but change of HPD use was not mentioned.

Lee et al. (2004) [36]

1) Standard intervention group participated in 10 educational activities on farm safety including interactive training, printed and electronic materials, discussions on activities in national forum and writing information for newsletter and 2) Enhanced intervention group participated in all standard activities and additionally received telephone calls, mailings, personal contacts and free personal protective equipment.

Nationwide program based in FFA did not result in changes in agricultural safety knowledge, attitudes, leadership, self-concept, or injuries. Program also failed to develop sustainable community partnership.

 • Intervention fidelity was poor.

 • Initial positive outcomes were not retained at 1 year.

 • No process measures observed in control group.

Joseph et al. (2007) [38]

1) Small-group training on the attenuation performance of formable HPD, 2) small-group training on the attenuation performance of premolded HPD, 3) individual training on the attenuation performance of formable HPD and 4) individual training on the attenuation performance of premolded HPD.

Both group and individual training formats demonstrated significant effect both types of HPDs on attenuation and attitude but the difference in attenuation between group and individual training was not significant.

 • There was no follow-up data collection and therefore, no evidence of sustained learning was obtained.

Berg et al. (2009) [33]

Hearing conservation program comprised of (i) classroom instruction at each school, (ii) distribution of HPD, (iii) direct mailings to the student’s home, (iv) noise level assessments at the student’s home, and (v) yearly audiometric testing.

Students in the hearing conservation intervention group reported more frequent HPD use but no post-intervention evidence of reduced levels of NIHL was observed.

 • Since NIHL is cumulative, a 3-year study was likely not long enough to evaluate the efficacy of this intervention.

 • The report lacked description of control group activities.

Kotowski et al. (2011) [39]

Brochure developed on the threats, severity and susceptibility of NIHL and efficacy of behaviors that can minimize the threats.

Viewing brochure improved perception of NIHL and efficacy to use earplugs without changing intention of HPD use.

 • Convenience sampling approach was used

 • Lacked statistical analysis as confounding variables were not taken into account.

Marlenga et al. (2011) [24]

Described above*.

Participants from the intervention group reported significantly higher use of HPDs in agricultural activities and greater use of HPDs for shooting guns than the controls. For other activities, both groups reported similar uses of HPDs.

No significant differences between groups with respect to objective measures of NIHL was observed.

 • The study lacked power when compared with parent study*.

 • Low enrollment rate at follow-up (i.e. 52% of the subjects was retained).

 • The study demonstrated limited effectiveness in preventing early NIHL in rural high school students at 16-year follow up.

Martin et al. (2013) [27]

1) Classroom presentation by older-peer educators (high school students), 2) classroom presentation by health professional educators (school nurses), 3) on-site museum visits interaction with a museum exhibition on NIHL and tinnitus prevention, and 4) virtual museum experience via internet.

Positive effects in knowledge, attitude and behavior in all formats of interventions were observed. In terms of effectiveness, the classroom programs were more effective than the internet-based virtual exhibit, which was more effective than the visit to the museum exhibition. Interpersonal, interactive educational interventions such as the classroom program are more effective and have longer impact than self-directed learning experiences for NIHL and tinnitus prevention.

 • Detail information about the process of randomization was not provided.

 • Duration (i.e. time spent) of the four different formats of intervention varied.

 • Validity of the knowledge questions was not addressed.

 • The study did not detect significant differences between groups perhaps due to weak statistical power.

 • No adjustment for sociodemographic variables was observed.

Gilles et al. (2014) [34]

A governmental prevention campaign ‘Anything less is the max’ targeting high school students via television and radio commercials, social media, posters and interactive website was used. Major emphasis of the intervention was placed on loud music, controlled use of personal listening devices and prevention approaches at other noisy situations.

Scores on the youth attitudes towards noise scale (YANS) and the beliefs about hearing protection and hearing loss (BAHPHL) decreased significantly after intervention. Hearing protection use increased significantly from pre to post intervention. Use of personal listening devices did not change.

 • Weak study design as there was no comparison or control group.

 • Effect sizes not reported.

 • Random sampling strategy was not used.

 • Time of post-testing was not specified.

Keppler et al. (2015) [40]

This education program was presented one-on-one between the audiologist and the subject using a structured slide show. It contained information about functioning of the normal auditory system, the effects of noise exposure on the auditory system, and the preventative measures including information regarding HPDs. Five questions were asked to the participants to evaluate the level of understanding. Audiometric evaluation was also performed on the subjects.

Educational intervention improved the hearing protection attitude, belief and frequency of HPD use. There was a significant decrease in recreational noise exposure between pre and post training sessions.

 • Study was conducted with a very small sample size (i.e. pilot study).

 • It used a wide range of time between pre and post intervention data collection for the participants.

Khan et al. (2018) [35]

1) Classroom training on noise exposure and HPD use, 2) classroom training on noise exposure and HPD use coupled with smartphone app training to measure noise levels during noisy farm tasks and 3) computer training on on noise exposure and HPD use.

All three formats of educational interventions improved hearing conservation and protection knowledge, attitude & HPD use within each group. When the groups were compared the changes of knowledge, attitude & HPD use between groups were non-significant.

 • Study was conducted with a very small sample size (i.e. pilot study).

 • Very short follow-up period was used and therefore, the sustained effects of interventions could not be measured.

 • Validity of instruments used to measure outcome variables was not reported.