<p>A motor assembly (100) includes: a suction motor (110); at least one inner casing (120) adapted to enclose at least a part of the suction motor (110); and at least one outer casing (130) configured to enclose at least a part of the at least one inner casing (120), wherein a diffusion passage (P1) is formed between the at least one inner casing (120) and the at least one outer casing (130) and has an average cross-section that gradually increases to allow air to diffuse therein.</p>
