As described, muttering under the breath would be less audible than breathing which, in most cases, would be about as loud as silence. If the mutterance were not meant to be heard, I imagine that the mutterer would merely think it.
As described, muttering under the breath would be less audible than breathing which, in most cases, would be about as loud as silence. If the mutterance were not meant to be heard, I imagine that the mutterer would merely think it.