Temporal echo

A temporal echo or time echo was a time disturbance with the past or future breaking into the present, described by the Third Doctor as "dangerous." (AUDIO: Storm of the Horofax) It was a space-time event in which those experiencing the echo could not be seen nor could they touch anything until someone outside the echo touched the object.

The Doctor and his companion Guinevere Winchester experienced a temporal echo on the Schrödinger Institute. (PROSE: Revenants)

The crew of the HMS Nemesis experienced a time echo where the sounds of fighting with futuristic weapons could be heard, although no battle was visible. (AUDIO: Storm of the Horofax)

When Ace saw another police box while the TARDIS was trapped in a temporal plexus, the Seventh Doctor called it a temporal echo. Because time and space were so mixed up where they were, she could've seen them ten minutes ago or a decade in the future. (PROSE: The Ripple Effect)

On one planet, the Second Doctor described an object which appeared to be a strange cloud as "an echo of some cosmic events across the corridors of Time." The army of humanoids entering the cloud were unable to see or hear the Doctor, and passed through him as if they were ghosts. Jamie McCrimmon followed them through the cloud and was almost made their leader in their battle against the Scythias. (PROSE: Follow the Phantoms)