TiVo would have to insert the sound effects into a DD stream, which would mean decoding it, adding the sounds, and then re-encoding it. The Dolby license doesn't allow for this, and it's probably too processor-intensive to do anyway (at least back in the Series 3 days.)
TiVo Mini X 3
Left DirecTV 4/15/07. Left TWC 8/8/11. Now on Comcast Xfinity.