Abstract: Vacuum cleaning apparatus, particularly adapted for wet/dry cleaning operations includes a powerhead housing assembly formed by an impeller housing for supporting an electric motor which drives a working air impeller and a motor cooling air fan and a cover member removably secured to the impeller housing. The impeller housing and the cover member define flow passages and chambers for diffusing and expanding working air flow to reduce noise emissions therefrom and for directing motor cooling air through the housing assembly without mixing with working air flow and while minimizing the ingestion of working air into the motor cooling air flowpath. An alternate embodiment of the housing assembly includes separable, opposed impeller housing members and a shroud member, all secured together by common fasteners and cooperating to form the working air diffusing and expansion chambers together with the cooling air flow passages.