THESAURUS
muttering
aspiration, bated breath, beefing, bellyaching, bitching, breath, breathy voice, complaining, complaintful, crabbing, crabby, cranky, croaking, disappointed, discontented, disgruntled, displeased, dissatisfied, drone, droning, envious, exhalation, faultfinding, gabble, gibber, gibbering, griping, grouchy, grousing, growling, grumbling, jabber, jibber, little voice, low voice, malcontent, malcontented, maundering, mouthing, mumble, mumbling, murmur, murmuration, murmuring, murmurish, murmurous, mutter, out of humor, peevish, petulant, querulant, querulous, rebellious, resentful, restive, restless, rustling, sigh, soft voice, stage whisper, still small voice, sulky, susurrant, susurration, susurrous, susurrus, unaccepting, unaccommodating, underbreath, undertone, uneasy, unfulfilled, ungratified, unhappy, unsatisfied, whiny, whisper, whispering, whispery