To my knowledge there is nothing you can do but re-record. There is no "dial application" that allows you to speed or slow the pace. I suppose if you had long periods of silence you could edit the clips to remove bits of silence to speed things up or you could introduce bits of silence to slow things down, but there is nothing overall that allows you to adjust pace.
Yesterday Giveaway of the Day offered a product called Audio Speed Changer. Sounds like something you may have been interested in. Had you known about it yesterday (or were following my Twitter feed) you could have obtained it at no charge.
Aside from that possibility, you might try adjusting the frame rate in Captivate. But I am very skeptical that will actually do anything for you audio wise.
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