Easy enough... just take your audio into whatever program you are using to handle it (SoundBooth, Audition, ProTools or whatever) and adjust the speed while maintaining pitch to the correct new speed.
What that exact speed is, i'm not sure. That will take a little math and testing. In a perfect world you could just say that taking your 25fps audio and adjusting it to 96% will give you 24fps... but it's not quite as clean as that. Your 24fps audio is acually 23.976fps of course... and the 25fps might not be true 25fps either, so a little experimentation is in order. Really easy in theory though.
Fantastic Plastic Entertainment, Inc. fantasticplastic.com