App note from Cirrus about overshoot/ringing suppression in the output stage of Class-D amplifiers using RC Snubber. Link here (PDF)
High speed switching of power MOSFETs in the power stage of Class-D amplifiers results in output voltage over/undershoot and high frequency ringing on the output waveform. The over/undershoot places additional stress on the power MOSFETs, potentially reducing MOSFET lifetime or, in extreme cases, causing avalanche breakdown.
The high frequency ringing can couple to nearby PCB planes and cables and is therefore a source of radiated emissions. Radiated emissions can be particularly problematic in portable electronics where the Class-D amplifier may be some distance from the micro speaker and connected by a relatively long unshielded twisted pair or flex cable.