Related Clues:

• Interjection to attract someone's attention without alerting others
• Whispered "yoo-hoo"
• Whisper for attention
• Alternative to a tap
• Subtle "Hey, you!"
• Sibilant sound to get someone's attention
• Covert summons
• Secretive "over here"
• 'You ... over there ...'
• 'What's up?'
• Bad attention-getter in a crowded bar
• Sound that turns some heads
• Soft "hey, you"
• Clandestine attention-getting sound
• Sound heard by an exam proctor, say