At what level does sound become unsafe?
It is strongly recommended, to avoid unprotected exposure to sound pressure levels above 100dBA. Use hearing protection when exposed to levels above 85dBA (about the sound level of a lawn mower when you are pushing is over a grassy surface), and especially when prolonged exposure (more than a fraction of an hour) is expected. Damage to hearing from loud noise is cumulative and is irreversible. Exposure to high noise levels is also one of the main causes of tinnitus. The safety aspects of ultrasound scans are the subject of ongoing investigation. Health hazards also result from extended exposure to vibration. An example is “white finger”, which is found amongst workers who use hand-held machinery such as chain saws.
