Every year 2-3000 incidents involving hearing loss are reported to Arbejdsskadestyrelsen. This makes hearing loss the second most commonly notified occupational hazard in Denmark. Hearing damage is irreversible, so that in itself should be a reason to protect your hearing.
Be aware that hearing damage can occur in several ways. Short term intense sonic pulses may be as damaging as continuous noise exposure.
There are no strict limits on when noise becomes unreasonable. However, there are indicative max. values of noise load. Whether noise is annoying is best assessed by those working in it and therefore it is up to you to tell your OSH rep if you have problems.
Noise can be reduced, therefore the use of ear defenders/earmuffs is an absolute last resort. If it is not possible to reduce noise by means of encapsulation or screening, you have to use earplugs or earmuffs/ear defenders. Always use earmuffs when working with ultrasound.
At the Institute, earmuffs are available beside all apparatus that generates ultrasound. In addition there are earplugs and earmuffs on the hanger.