The echo is your voice returned by the world — the word sent out arriving back changed only by distance. Dream-echoes concern what you put out coming back: the call answered only by yourself, the repetition that mocks or confirms, the space measured by return.
Positive Resonance
The world responsive, the self heard back, space sounded
Shadow Aspect
Only your own voice answering, the echo chamber's closed loop
Nuances
Calling and hearing yourself: the world returning only you
The echo delayed: response across great distance
Words repeated back wrong: the message distorted in return
Silence instead of echo: the void that does not answer