We have tested a number of double-hung windows with different glass types. Windows fitted with ‘Qlon’ seals horizontally and weatherpile vertically with 5mm glass gave 27dB(A) RW28 sound reduction, 6.38mm laminated gave 27dB(A) RW28, 7.52mm laminated glass basically gave the same result at 28dB(A) RW30. For the best sound reduction go to SoundOUT™ awning or sliding windows.