Life On Mars constantly uses the motif of hospital and 'real world' noises to portray the idea of sam not being fully in the world he's been placed in. It's to hint that he might not actually have time travelled, or he has and someone is communicating with him.

It's presented as a dream like soundscape, fading in and out, with 'outside' noises such as Life On Mars on the radio in this scene. 

I like this motif, and I think it lends itself well to our idea of having the noises of the hospital fading in and out of the mother's subconscious as if she is daydreaming or has more important stuff on her mind. 

I am going to continue my analysis of individual scenes as I go through the DVD as there aren't many scenes available online. They use different ways of communicating the sound so I am going to explore this.