Ensuring the individual effectiveness of hearing protection as a contribution to the inclusion of people with hearing loss

Status:

completed 03/2021

Aims:

Goal of this project was to secure an optimal provision of hearing protectors for the workplace not only for normal hearing persons, but also for individuals with mild or moderate hearing loss. Moreover, the selection process should be based on suitable criteria for the target group.

Activities/Methods:

Different aspects of selection and use of hearing protectors for hearing impaired persons were investigated in five work packages. In work package no. 1 a survey was performed with 149 hearing impaired users of hearing protection. In addition, speech intelligibility tests in noise with and without hearing protectors were conducted for 92 workers in the companies. Work package no. 2 investigated the usability of level-dependent hearing protectors, also based on speech intelligibility tests in noise. In work package no. 3 the individual protection performance of hearing protectors was examined since it is known that hearing protectors yield a clearly reduced sound attenuation in real world compared to the type examination. It was tested if the determination of the individual sound attenuation using audiometers is suitable for field-use. Own measurements under laboratory conditions were performed and measurements of 119 persons by occupational physicians were analysed. Work package no. 4 addressed the issue that the certification procedure of hearing aids for noisy work places is fairly complicated, resulting in only one manufacturer on the market so far. Thus, the work package had the aim of defining a more flexible approval procedure for this kind of hearing aids. Finally, in work package no. 5 the current implementation of individual prevention measures for noise (IP Lärm) at the German social accident insurance institutions was determined. Based on these results, recommendations for further developments could be derived.

Results:

The survey yielded that the majority of hearing protector users with a hearing loss are satisfied with their hearing protector. It needs to be noted that ca. 55% of the participants were provided with custom moulded earplugs. Signal audibility with hearing protectors is generally good, while communication was satisfactorily possible for half of the participants. For the other 50%, conversations were only partially possible or not at all. Even more challenging were telephone calls, that were only completely possible for 10% of participants.

The speech intelligibility tests in noise showed a significant reduction in speech intelligibility for the measurement with hearing protector compared to the situation with open ears. This is especially true for the subgroup of participants with more severe hearing losses. This group, on the other hand, had the largest positive effect on speech intelligibility by using a level-dependent hearing protector in the active mode.

The determination of the individual sound attenuation can be achieved with suitable accuracy also in companies with screening audiometers. According to the participating occupational physicians, the necessary additional audiometric measurements can be incorporated into the established occupational medical prophylaxis. The analysis of the acquired individual sound attenuation data showed that the values are strongly reduced compared to type examination results, especially for roll-down foam earplugs. Two newly produced publications (DGUV informative publication 212-003 and European standard EN 17479) support the user of individual fit testing systems with guidance to selection and use of these systems.

The approval procedure for hearing aids for noisy work places has become more flexible due to the newly developed documents DGUV Principle 312-002 and the IFA principles on testing and certification GS-IFA-P16. The result are so-called combinable hearing aid systems.

Moreover, a revision of the IFA principles on testing and certification for complete hearing aid systems for the workplace (GS-IFA-P14) defined requirements for these products more precisely. An individual prevention programme for noise (IP Lärm) is not yet practised by all German social accident insurance institutions at the moment. A guidance document by DGUV describes a procedure with visits to the company and to the individual with hearing loss. In addition to that, some German social accident insurance institutions offer special seminars for individuals with hearing loss.

The results of the whole project show on the one hand that there are several possibilities to adequately provide hearing impaired persons with hearing protection, i.e. to protect the residual hearing ability and avoid a job change. On the other hand, it can be derived which aspects of individual hearing conservation for hearing impaired persons are already established successfully in the companies and at the German social accident insurance institutions and which need to be promoted further. This includes annual instructions with practical training as required by DGUV Regulation 1 for hearing protectors as personal protective equipment of category III.

German social accident institutions (UVT) can gain suggestions from the results of the project regarding which stakeholders in occupational safety and health (the institutions themselves, employers, safety engineers, occupational physicians, employees) could be included in a successful provision with hearing protectors for hearing impaired persons in a suitable manner.

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