OSHA Says you must put on ear safety for sounds in excess of eighty five decibels. A fuel garden mower is all over ninety decibels. However, the Centers for Ailment Command and Avoidance (CDC) states that regular publicity to sounds more than 70 decibels can result in some hearing destruction. https://reiddtbba.blogrelation.com/38593044/sound-level-meter-fundamentals-explained