Echo Sphere
From Tardis Wiki, the free Doctor Who reference
The Echo Sphere The Echo Sphere was a self contained environment, a protective shell for the inhabitants sealed within their planet. These quiet and gentle bird-like creatures were known to occasionally break into very quiet, very gentle songs would echo around their little world for hours because of the Echo Spheres ability to magnify sound and act as a natural echo chamber. (DWAM: Bad Vibrations)