Damping rates add directly while quality factors do not

Evidence

If there is more than one source of friction, it is clear that the damping will be larger and the Q smaller than with either source alone. Damping simply adds: dtotal = d1 + d2. But Q α 1/dtotal (see section 10.3), so different Q’s don’t directly add but instead satisfy On resonance, two key factors are in a tug-of-war. — Eric J. Heller, Why You Hear What You Hear- An…, 1039