According to SummitRacing.com, a COMP Thumpr cam is nasty and muscular with a harsh-sounding idle. The camshafts give vehicles a powerful, gruff exhaust note with high horsepower and torque at varying revolutions per minute.
A review from January 2015 on SummitRacing.com describes the sound of a COMP Thumpr cam as an aggressive rumble, and a reviewer from May 2015 says the camshafts provide a bottom-end thump.
According to the site, an early exhaust valve opening, a long-lasting exhaust, and a lot of overlap between intake and exhaust combine to create the idling sound. The camshafts produce the exhaust note without detracting from the power of the engine.