At 25fps and 48Khz you rather neatly have 1920 samples per frame, which is coincidentally the width of an HD picture. At least I think it's a kind of a coincidence... I believe the number 1920 was derived from the 720 horizontal pixels of Rec. 709, which doubled give a 1440 pixel 4:3 picture and hence a 1920 pixel 16:9 picture.

The 48Khz rate used by everything apart from CDs also came from video standards according to http://www.tvtechnology.com/opinions/0087/digital-audio-samp...

Here's some more about the number-theory used in digital video, from 1990 during the standardisation of HD: http://www.poynton.com/papers/SMPTE_90_Magic_Numbers.html