A power unit for an in-wall vacuum cleaning system has a first compartment which contains a motor for producing a vacuum at remote wand receptacles and a second compartment for separating and collecting the debris. An improved sound reducer is mounted in the motor compartment for reducing the sound level emitted by the motor and providing good cooling airflow for the motor. The sound reducer includes a disc-shaped base having a central opening for receiving a portion of the motor and a pair of partitions mounted on the base and forming a plurality of irregularly-shaped sound passages for breaking up the sound waves traveling therethrough. The base and partitions are formed of an acoustic foam which assist in absorbing the sound waves.