A multi-ribbed power transmission belt having longitudinal grooves and transverse
grooves that form a plurality of cogs on the belt surface defined between adjacent
transverse grooves is provided. The pitch lengths of the rows of cogs are randomized
or sequenced over the entire length of the belt to reduce the noise of the belt
as it travels about its associated pulleys. The ideal pitch pattern on a belt is
variable, dependent upon the circumferential length of the belt. To create an optimized
pitch sequence for belts of various circumferential lengths, a method of manufacture
is employed wherein a portion of the pitch sequence of a shorter belt is incorporated
within an optimized pitch sequence of a longer belt and both belts are manufactured
from a single mold. The longer belt may contain cogs of various shapes intended
to offset a range of frequencies and minimize noise generation. By selecting a
certain span of the longer belt for the creation of smaller belt(s), a single mold
may be utilized for producing belts of varying length and the noise characteristics
of the belt may be controlled and optimized.