Related Clues:
- Refrigerator noise
- Complaint odds have been switched
- Odds on returning drone
- Air-conditioning sound
- Drink repeatedly being knocked over leads to grumble
- Speak softly or indistinctly
- May sounds with a closed mouth
- Sing with one's mouth closed
- Not quite sing
- Drum starter?
- Vocalize on a kazoo
- Sing with a closed mouth
- Smell and sound of bees
- Smooth machinery sound
- Half the people on earth smell