Doctor Who: 10 Things Everyone Always Gets Wrong About The TARDIS
4. Where That Wheezing Noise Comes From
That distinctive grinding and wheezing sound is the TARDIS' dematerialization circuit engaging. Ace once referred to it as a key being dragged along a wire, while the Moment (as portrayed by the Bad Wolf/Rose Tyler), said that the wheezing sound gives hope to all who hear it, no matter how lost they are.
When the TARDIS matrix was forced into Idris in The Doctor's Wife, she used the sound to identify herself to the Eleventh Doctor. LINDA’s Elton Pope called the sound “the most beautiful sound in the world”, and Kate Stewart even had the sound as her ringtone.
In other words, you'd think that this sound is just a normal part of the TARDIS - so it was quite strange when River Song claimed that the noise only happened because the Doctor left the brakes on.
Now, this could very well be true, but other TARDISes (including the Master’s) have made that sound in the past, and furthermore, the Doctor has deliberately landed the TARDIS in silent mode on several occasions - once in the Oval Office to avoid drawing attention to himself, and once on Trenzalore to avoid making a fuss, despite the Doctor’s personal belief that the noise is “brilliant.”