Abstract: A commutator has a plurality of spaced, electrically conducting segments, each of which has a physical dimension determining the relative time duration of brush contact with said segment during commutator rotation with audible brush noise being generated between the brush and said consecutive segments, the noise including a fundamental frequency component at a frequency related to the frequency at which the consecutive segments pass the brush. The physical dimension of the consecutive segments varies from each segment to the next according to a predetermined pattern effective to vary the relative time of brush contact from each segment to the next during rotation and thus reduce the amplitude of the fundamental frequency components to make the brush noise less tonal in character and thus less annoying.

Abstract: Two spaced capacitors are connected in parallel across each supply lead of a brush-commutator type electric motor and the motor frame to provide a PI filter for each brush in which the length of brush lead between the capacitors comprises the inductor element of the filter. To facilitate this arrangement, one of the capacitors for each brush is mounted upon one side of an annular support member of an insulating material and an electrically conductive plate arranged to electrically engage the motor frame upon assembly is mounted upon the other side with electrical connections extending through the support member to interconnect one terminal end of each of the capacitors to the conductive plate and to secure the conductive plate to the support member.