I speak without a mouth and hear without ears. I have no body, but I come alive with the wind. What am I?

An echo is the correct answer because it represents sound reflecting off surfaces and being heard again. It doesn't have a mouth to speak or ears to hear, but can only exist when sound waves bounce back to our ears. The mention of needing the wind indicates that movement (wind) enables sound travel. This riddle exquisitely captures the abstract nature of natural phenomena using personification and metaphor.