How loud is a 50 cal sniper rifle?

It has been reported that the muzzle blast "sound" of a .50 BMG is at or above 180 decibels at a distances up to around 5 feet. That is enough overpressure to cause permanent hearing loss. Note: adding a muzzle blast deflector/muzzle break to the barrel of a .50, directs the pressure wave at an oblique angle along the axis of the barrel. In other Words - you don't want to stand, sit or lay prone outside the angle of that blast when the weapon is fired.