Fake crowd noise
Down here in Australia, we're lucky enough to be able to watch my favourite sport, AFL (Aussie rules football).
Due to there being no spectators in the stands, they've started using fake crowd noise when watching on tv. A lot of folks are dissing this but personally I find it quite effective. The guys are getting really good at it too, and are using the right sounds in the right moments. It's almost become an art form.