With the implementation of the new ordinance on noise and vibration protection, the values for prevention have been decreased. Engine drivers/shunters work partly under strong and threshold exceeding noise. The importance of audibility of warning signals causes, that hearing protection is not always used by every engine driver/shunter. There is a mathematical method to sort the hearing protection in different groups with different tolerances. In addition to the mathematic procedure, it is necessary to perform an individual hearing test according to BGI/GUV-I 5147 to guarantee the adequate perception of the signals. This investigation shall be added to the existing procedure which is very time consuming and complex. The purpose of this investigation is to make sure, that warning signals are not impaired by hearing protection. The hearing test shall be done in a room with normal acoustical conditions where the situation on the rail and loco shall be adopted as realistically as possible.
To perform the hearing test under most realistic conditions in a normal room, all relevant acoustic signals (warning and interfering signals) need to be recorded on the rail with head-based measurement equipment. The test signals are evaluated binaurally by the engine driver/shunter. A 2AFC (two alternative forced choice) method is used for the panel test. The developed software detects the masked threshold of the test person by classification of their answers. At the end of the investigation, a panel of engine drivers/shunters shall perform the test according to BGI/GUV-I 5147 as well as the new hearing test. Therefore, both results can be matched and the new method can be validated.
The new testing program shows differences the hearing exercise according to BGI/GUV-I:
The variability of the interference noise, as enabled by the testing program, and consequently the close approach of the acoustic environment to reality do require a considerably higher degree of attention and concentration over a longer period of time than it would be necessary in the hearing exercise according to BGI/GUV-I 5147. There is a greater chance than in the hearing test of BGI/GUV-I 5147 that a hearing protection system will not pass the audio test due to the slightly higher requirements on the proband’s skills. It might happen that some probands will have to repeat the audio test after a short break if they cannot manifest the required concentration instantly in the new and unfamiliar hearing situation.
trafficDescription, key words:
warning signals, hearing protection, engine driver/shunters