A ventilated brake rotor (24) includes vent holes (42) between inboard (32) and outboard (34) friction plates. The vent holes (42) are separated by ribs (40) spaced in regular circumferential increments about the rotor (24). The rib pattern (40) is divided into two or more sectors (48) of equal angular measure. Within each sector (48), an attenuation region (50) interrupts two or more ribs (40) by replacing the ribs (40) with a cluster of individual pins (54) which may be arranged in radial and circumferential rows. Each attenuation region (50) spans a territory within each sector (48) that is preferably at least 20% and less than 55% of the sector (48) real estate. The rotor (24) completely or at least substantially eliminates vibration modes in objectionable, audible frequencies without adversely affecting the structural integrity, cooling capabilities or functional attributes of the disc brake assembly (22).