audio showing silence where words are in slide timeline view

Hi.   When I double click on audio on the time line  edit it to add a few seconds of silence, it does add it.  I then click save and close.  When I look at the soundwave on the slide timeline, the visual rendering of the soundwave isn't in sync with the actual sound.   (what looks like silence, for instance, actually has sound).   I think it's just skewed a bit, but it makes it hard to line things up on the timeline as most picture transitions start during a period of silence.

How can I fix this?

Thanks,