By muffler you mean silencer. Silencers are almost a metre long. All the fans i've seen even fans in shop that people say are silent are noisy as fuck. I duno why people say that these fans are quiet when the airflow sounds like a gale which is more than noticable if placed near a wall, you can hear the air flow and cool running through solid brick walls and through solid brick roofs so your version of quiet running is very different from mine. Used in a wardrobe these fans make a fucking racket enough for the neighbours to say 'what's that humming' and in my opinion that is not quiet running. What other options are available for people who want to use the smallest extraction fans in very small enclosed spaces and want serious noise reduction. Even pc fans are noisy in very small grow rooms.