Protection against noise for engine drivers and engine driver/shunters

Status:

completed 03/2011

Aims:

With enactment of the new German Ordinance on noise and vibration protection (LärmVibrationsArbSchV), the action values for prevention measures have been lowered by 5 dB(A). Hearing protection must now be made available from a daily noise exposure level of 80 dB(A) upwards, and worn from 85 dB(A) upwards. The hearing protection for engine drivers and engine driver/shunters, where it is necessary, must however not obstruct communication or the perception of signals. For this reason, the wearing of hearing protection has not been permitted in the past by the labour inspectorates responsible for the railway sector.
The objective of this project was to develop a method for the selection and use of hearing protection which could be supported by the labour inspectorates responsible for the railway sector.

Activities/Methods:

The project studied the suitability of hearing protection at railway workplaces. A selection procedure based upon the procedure followed for work on the permanent way and for drivers of vehicles on the public highway proved suitable. The selection procedure uses mathematical analyses to test whether a hearing protector enables signals to be adequately perceived and communication to take place unhindered under the given background noise conditions. In addition to this initial, mathematical selection, a hearing test must be performed at each site under realistic conditions in order to guarantee adequate perceptibility of the signals.
Results from a parallel project (IFA Project 4152: Protection against noise for engine drivers and engine driver/shunters) were used for this purpose. Project 4152 measured the noise exposure of engine drivers and engine driver/shunters. The project also considered work procedures relevant to safety, and the associated need for signal perceptibility. The relevant acoustic signals and the necessary communication were analysed with regard to their frequency composition.
The method used in the project described here for analysis of the signal audibility is based upon spectral masking according to Zwicker (ISO R 352 Part B). For this purpose, the signal perceptibility is calculated with and without hearing protectors for all combinations of signals and background noise. If the signal perceptibility is significantly impaired by the hearing protection, the latter is not suitable for use at the workplaces concerned.
A method also had to be developed for a personal hearing test at the workplace.

Results:

18 safety-related signals and noises and 12 work noises were selected from the results of the operational measurements. These signals and noises were used to calculate the signal audibility according to Zwicker for all hearing protectors on the IFA's list of approved products (the list of all hearing protectors with EC type examination certificate reported to the IFA). This procedure found that 13% of the hearing protectors were suitable for the hearing of signals at railway workplaces.
Parallel to these measures, a method was developed in the project working group for a personal hearing test at the workplace, and trialled in pilot field tests.

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