The term 'Cave Sound' can be broken down into three crossword solutions: ECHO (4 letters), ECHOES (6 letters), and Ayla (4 letters). ECHO is a sound that is created when sound waves are reflected off of a surface, such as the walls of a cave. ECHOES are the repetition of this sound, which can be heard in caves due to the enclosed space. Ayla is a type of ECHO chamber, which is a man-made structure designed to amplify sound.