Miele DA 390-6 Operating Instructions Manual page 40

Connection for air extraction
Air extraction with external motor
To minimise noise from the motor in the
kitchen, the silencer should be
positioned in front of the external motor
 if possible, or, if the ducting is long,
above the exhaust connection inside
the rangehood . In the case of an
external motor located inside the
house, fitting a silencer behind the
external motor  reduces the noise of
the motor outside the house.
40