Sound deadener (7)
(Other definitions for earplug that I've seen before include "Noise defender" , "Block" , "Hearing protector" , "Sound excluder" , "Protection from sound" .)
(Other definitions for muffler that I've seen before include "Warming garment" , "Wrap or scarf worn round the neck" , "Thick scarf - silencer (US)" , "Sound deadener" , "Kind of scarf" .)