Related Clues:

• Noise at night
• Concern for some sleepers
• Statistician's problem
• Sleeper's problem
• Empty information
• Boom, vroom, or zoom
• Reason for earplugs
• Dull thing, in slang
• Nighttime problem
• Sleep-clinic study
• Go ''ZZZ!''
• Sing & ___ Ernie ("Sesame Street" doll)
• Crash accompanier
• Nighttime breathing disorder
• Construction-site by-product