This is the first time the roll-back-and-mix effect is used in studio to show the Police Box appearing. Notice also this was back in the early years when the TARDIS materialisation was completely silent.
If you're interested in learning more about how the TARDIS noise evolved, visit www-themindrobber-co -uk
This is the first time a landing sound effect was used for a landing, instead of a take-off sound being used for everything. If you're interested, read more at www-themindrobber-co -uk