Dishwasher appliance pump motor cover acoustic tuning

A dishwashing appliance defining a vertical direction, a lateral direction, and a transverse direction, the dishwasher appliance comprising:

• a tub defining a wash chamber;
• a door mounted to the tub to provide selective access to the wash chamber;
• a rack mounted within the wash chamber and configured for receipt of articles for cleaning;
• a spray assembly;
• a supply conduit fluidly coupled to the spray assembly;
• a pump assembly fluidly coupled to the supply conduit, the pump assembly comprising:
• a housing supporting an impeller for rotation within the housing;
• a motor coupled to the impeller to impart rotation to the impeller;
• and
• a cover affixed to the housing, the cover comprising a first panel, a second panel positioned within the first panel, and a beam extending between the first panel and the second panel, the cover defined between an inner surface and an outer surface, the first panel and the second panel spaced apart by one or more openings formed through the inner surface and the outer surface of the cover,
• wherein the beam defines a first end adjoining the first panel to the beam, and a second end of the beam adjoining the second panel to the beam, the second panel entirely spaced apart from the first panel by the one or more openings, and
• wherein a length of the beam along a longitudinal axis defined by the first end and the second end of the beam is at least twice as long as a width of the beam defined perpendicular to the longitudinal axis.