Miele DA 2558 Operating And Installation Instructions page 51

Connection for air extraction
Recirculation mode
The silencer needs to be positioned
between the exhaust socket and the
exhaust grille . Ensure there is
adequate space for fitting it.
Extraction mode 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 socket on the cooker
hood . 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.
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