sprinkle bicarb of soda over the area leave for a while and vacuum off, though if it has soaked right into the sound proofing behind the carpet then you may have to get a steam cleaner and use that.
the only way. When area is wet sponge with soda bi carb mixed in water. allow to dry then rub in the soda bi carb leave overnight then vacuum or brush out can be repeated.
Its brill for all stinky smells on carpet and such. For puppy accidents blot up then splash soda water on prevents stains and smells