Related Clues:

• Runs smoothly, as an engine
• Stomach muscles
• Sounds of relief
• Massage reactions
• Engine sounds
• Sounds from spas
• Physical responses?
• Soothing sounds
• Runs smoothly
• Contented sounds
• Sounds from the hot tub
• Depressing sounds, to a doctor?
• Gasps of delight
• Sighs of contentment
• Sounds of understanding