Default Display for Voice Tags

Currently the spec doesn't talk about anything related to a default display for voice tags. The way it's set up now is for voice tags to be converted to <spans> with a "title" attribute that is the voice of the speaker. Normally this would mean that when you mouse over the span we would see a tooltip. However, this functionality currently isn't working in Webkit as far as I can tell and to implement it in Firefox would take some work.

My question is if there should be a default display for Voice tags such as "Voice: Text" or something like that or is it being deliberately left up to the author of the WebVTT to specify some kind of display through CSS? Is the tooltip supposed to be the default display?

Rick