This can often be called temporary threshold shift and is where a person has been exposed to noise over a period of a few hours and when they have left the noise area they encounter a muffled or dull sound with their hearing.
The hearing should return to normal but it can take up to 12 hours or so before it is back to normal. Many people encounter this problem when they have been to a loud nightclub or concert and describe their ears as ringing afterwards.
However repeated exposure to loud noise, even for these relatively short periods, can cause permanent rather than temporary damage to the inner ear.