Related Clues:

• Driver's nonverbal 'hello'
• Tugboat noise
• Traffic complaint
• Goose's sound
• Short blast of a whistle
• Bumper sticker word
• Train-whistle sound
• Whistle-blower's sound
• Tugboat's call
• Electrical sound
• Warning from a driver
• Voice-mail sound
• Start of many a bumper sticker
• Microwave call
• Electronic signal