Page 39 - OHS, March 2020

for sure when and where they occurred. It also means that the true noise sources are measured at the same time as the dose percentage, and the average noise levels are being collected. This leads to much more useful and accurate determinations of the likely harmful exposure frequencies and hence a more accurate choice of the right hearing protectors for the worker.
Vibration Sensors and
Other Improvements
There is always the possibility that the mi- crophone may get knocked during the mea- surements, leading to erroneous results for the true peak level and possibly over-esti- mating the time average result. Some mod- ern dosimeters feature a self-monitoring vibration sensor that marks samples during the run when the dosimeter is knocked or bumped accidentally (or deliberately) and these results can be identified in the soft- ware and removed after downloading.
The vibration sensor in the dosimeter serves another useful purpose: monitor- ing when the instrument is not being worn. This helps to alert when the operator may have taken it off and set it down. The do- simeters can detect when the instrument is being worn even if the operator is just sitting at a bench working normally. These dosimeters can provide very useful infor- mation to the IH looking to be sure that nothing out of the ordinary has occurred.
In the beginning of personal noise do- simetry measurement, the available instru- ments simply provided an overall noise dose percentage result based on one of the protocols specified by the regulatory bod- ies around the world. Gradually, more re- sults were included to better represent the measurement to give more insight into what had occurred including peak levels; maximum levels; time average levels; and normalized, time-weighted average levels. Different protocol measurements required repeats of the measurement to gain the right information about a worker’s expo- sure patterns, and this could take two or three days to collect.
Current noise dosimeters feature mul- tiple “virtual noise dosimeters” inside a single instrument by carefully splitting the acoustic path into two or three or more separate profiles configurable by the user. This way, a single measurement can now produce results calculated by the different required methods: OSHA, ACGIH, ISO, or
even a user’s own in-house protocol. One measurement saves time and effort by col- lecting all results in parallel.
Newer dosimeters also feature Blue- tooth communications for use with a dedicated app on a smartphone or tablet to review the accumulated noise exposure any time during the shift without having to interfere with the worker. This is a great practical advantage and enables the IH to see what the exposure levels are in the mo- ment without worker interference. If an above-the-limit noise is identified, workers can be given alternative, quieter tasks for the remainder of the day.
Conclusion
Modern noise dosimeters are small, light- weight, and feature multiple virtual in- struments. With all of these advantages these questions sometimes arise: Where do we go next to protect our workforce even better? What will the future hold for the next generation of noise dosimeters? We’ll certainly keep our ears and eyes open to find out.
Bob Selwyn is the North American Sales Consultant for the Svantek Sound and Vi- bration Products at Sensidyne.
www.ohsonline.com
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