Theoretically, a relatively inert (softer polymer) dustcover absorbs airborne sound waves--when closed, attenuating them before they reach the air around the tonearm, cartridge, stylus, plinth, and turntable base. That said, I use a Linn LP12 with the original dustcover; and I can’t discern a difference in SQ between listening with the cover off and listening with it closed. So I follow my dealer’s recommendation to listen with the cover closed.
Then again, my tin ears” can’t tell what color the walls in my listening room are painted either.
ASSOCIATED EQUIPMENT:
:Linn Akito III Tonarm
Linn Kandid MC Cartridge
Anthem STR Preamp (using integrated MC phono preamp)
Black Ice F35 (valve) Amp
Martin Logan EM ESL (electrostatic) Speakers
Martin Logan Dynamo 800X Sub
Audio Magic Interconnects
Off-white Listening Room.😉