The new Vents Acoustic fans are very powerful and quiet running - particularly for the large amount of air they move! Avaliable in five sizes to suit your needs. Avaliable in five sizes, not only can the KSA Acoustic fans move a large amount of air, they are very quiet running. It is the Acoustic lining in which the rotary motor is covered that helps to ensure that the Acoustic fans are quiet running. When combined with Acoustic fan speed controllers, noise levels can even be reduced in proportion to running speed. With a right-angled shape, the Acoustic fans are also lightweight and compact to fit into the smallest growing area.