Supervision of and support for Project FF-FP 410 on “Lärminklu” (noise inclusion)

Status:

completed 11/2020

Aims:

At present, hearing protectors are generally selected on the assumption that the wearer's hearing is unimpaired. Little consideration if any is given to persons whose hearing is already impaired. Where the wearer's hearing is already impaired however, hearing protection in the form of a personalized protective measure is likely to be effective only if it is tailored to the user's impaired hearing ability. In the first instance, this means safe protective action assured by adequate sound attenuation under real-case conditions, but also reliable perception of warning signals (such as from fork-lift trucks) and adequate speech intelligibility for communication. Only if these criteria are met will the hearing protector be used continually during noise exposure. A range of measures may be considered for the various aspects of selection and provision of hearing protection for persons with impaired hearing: determining the sound attenuation for the individual, use of hearing protectors with supplementary electronic functions or hearing aids for high-noise workplaces, and personalized prevention measures taken by the accident insurance institution. All these measures required studies of their effectiveness and acceptance.

Activities/Methods:

As part of the DGUV-funded project FF-FP 410, Ensuring the individual effectiveness of hearing protection as a contribution to the inclusion of people with hearing loss (LÄRMINKLU), the measures stated were examined by LGC-PS (Lärm- und Gehörschutz-Consult Peter Sickert). The IFA partnered with and supported the researcher. The IFA's work packages included:

• A literature study on the limitations of use of derating values for the sound attenuation level for persons with impaired hearing
• Laboratory measurements concerning the suitability of audiometric methods for determining personalized sound attenuation for the individual
• Support in the design and evaluation of surveys of persons with impaired hearing on their ability to communicate whilst wearing hearing protection
• Support in the design and evaluation of speech tests in the company, with and without hearing protection
• Participation in the development of an approval procedure for special hearing aids for use as PPE or in combination with hearing protectors at high-noise workplaces
• Trialling of speech audiometric procedures for assessing the suitability of hearing aids and hearing protectors at high-noise workplaces

Results:

The concluding report of the full project can be called up at the project website of project FF-FP 410. The following results can be ascertained from the IFA's work packages:

• The literature review revealed that the application of derating values during the provision of hearing protection to persons with impaired hearing had not yet been investigated systematically with regard to its suitability. Since, for this group of persons, the residual sound levels under the hearing protector must be set as precisely as possible, universal correction values are not a suitable measure; instead, the sound attenuation should be determined individually for each wearer.
• The audiometric method for determining personalized sound attenuation for the individual can also be used in the field in companies when screening audiometers are employed. In future, this method will be included in the "Noise" recommendation (formerly specification G20) for determining the personal protective performance and for medical consultation.
• LGC-PS surveyed 150 people with impaired hearing with regard to their experience with hearing protectors. The statistical analysis of these data by the IFA showed most of those questioned to be satisfied with their hearing protectors. The hearing of signals and conducting of conversations are usually possible, with a little listening effort; telephone calls are however not possible.
• The comparative language tests conducted in the companies by LGC-PS were validated in the IFA's laboratory. The Göttingen Sentence Test (GÖSA), which takes the form of a word versus sentence score, and comparison of the GÖSA and the Oldenburg Sentence Test (OLSA) were performed for this purpose. The following were performed:
  
  1. Comparison between the wearer's own hearing protector and open ear
  2. Comparison between a level-dependent hearing protector in active and passive mode

• The hearing protectors were shown to have significant effects, particularly for persons with moderate or more severe hearing loss. Speech intelligibility was seen to be poorer with the wearer's own hearing protector than without a hearing protector. Speech intelligibility was better with the level-dependent hearing protector in active mode than in passive mode. The GÖSA yielded similar results in the laboratory to those of the OLSA, but with poorer discrimination. However, for evaluation in the form of a sentence score, it proved easiest to implement in companies.

• A two-step process was developed for the approval of hearing aids for high-noise workplaces. The earpieces are certified as PPE in accordance with the new GS-IFA-P16 test specification. These products may be combined with hearing aids that comply with DGUV specification 312-002.

The project as a whole showed all approaches studied to be suitable for ensuring that persons with impaired hearing are provided with appropriate hearing protection. Experience in the field identified further potential for improvement in several areas. For this reason, the results of the project are to be published in a range of media with consideration for specific target groups (accident insurance institutions, companies, OSH professionals, company physicians, members of the CEN standards committee).

Last Update: