I don't have specific regulations and guidelines in front of me, so consider this as approximate summary of US OSHA guidance. I would guess that ISO regulations are similar. You can do your own research to confirm. Hire a qualified consultant to be sure. Don't take chances: hearing loss is permanent.
If I recall correctly, after a noise source in a work environment produces a level of 84(??) dBA, then noise protection is required of workers exposed to that noise level. At some point (dBA level) a formal hearing protection program must be implemented. Mitigation of the noise hazard should follow the order of precdence:
[ul]
[li]Elimination of the noise hazard[/li]
[li]Engineering solutions to reduce or eliminate.[/li]
[li]Administrative methods to reduce (e.g., work schedules, SOPs, reduce-by-distance, etc.)[/li]
[li]Personal Protective Equipment (and keep in mind that hearing protection is rated for noise attenuation levels so all devices are not equal)[/li]
[/ul]
Worker noise exposures are assessed by a Time Weighted Average TWA calculation and limited by Permissible Exposure Limits PELs.
If the work environment has multiple noise sources (e.g., a work cell with multiple machines generating noise) then there is a specific calculation method to determine the net resultant noise level to which the worker is exposed. It is NOT additive due to the nature of noise/sound. For example, an increase of 3dB of measured sound level is a doubling of the noise. Noise levels are also dependent upon the distance from the source.
TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering