The phrase "muted growl" refers to a quiet and restrained sound similar to that of a growl, which typically suggests anger or annoyance. Full definition
The eight - cylinder makes for visceral acceleration, but the S7 is very much a well - mannered beast with a muted growl, linear power delivery, and supreme smoothness. (automobilemag.com)
There's a muted growl when you really start to work it, but it's not a noise that has you deliberately holding onto each gear just to hear it again. (evo.co.uk)