Related Clues:

• Twice-heard sound
• Grotto sound
• Bouncing sound
• Outer edge
• Cave phenomenon
• Stairwell sound effect
• Salty spot on a margarita glass
• ''Hello'' again?
• Yodel recall?
• Agree with
• Voice agreement with
• Hoop edge
• Bounced response
• It may be heard in a tunnel
• Empty-hall sound