Grotto sound (4)
I believe the answer is:
echo
(Other definitions for echo that I've seen before include "Repetition of sound" , "Return of sound waves" , "Bounced sound" , "Repeat or reverberate" , "from Brussels?" .)
I believe the answer is:
echo
(Other definitions for echo that I've seen before include "Repetition of sound" , "Return of sound waves" , "Bounced sound" , "Repeat or reverberate" , "from Brussels?" .)