Related Clues:

• Malfunction indicators, perhaps
• Poltergeist's output
• Bangs and clangs
• Unmusical sounds?
• Some urban pollutants
• They may keep you awake at night
• Creak, squeak, and shriek
• I must interrupt film ogre's screams
• More than one unwanted sound is conveyed in refusals
• Bangs but not eyebrows, say
• Tennis shoe missing? Then, rackets!
• Various cacophonies
• Bumps in the night, e.g
• They break the silence
• Strange sounds