Related Clues:

• It always returns your calls
• Nymph rejected by Narcissus
• Sound that rebounds
• It's often tested with "Hello!"
• Effect of a yodel, perhaps
• Reflection of sound wave
• Narcissus's mythical partner
• Chamber effect
• Reflect sound
• Be in complete accord
• Make a comeback?
• Letter between Delta and Foxtrot
• Sound repetition
• Noise heard again
• Bounce back, in a way