Water leaking from bottom

There is usually a water cut off , behind the refrig , mounted on the wall , or , a cut off under the sink , connected to the cold water line ( with a small cut off valve ) .
The hissing noise , is usually associated with a hole or cracked water line . You can also try removing the ware filter , to see if the noise stops .
Would need more info , to have an idea where the water line is defective .