Here are the details from one of my DV files as downloaded from the camera. I'm using NTSC.
DV, 720 x 480 (640 x 480), Millions
16-bit Integer (Big Endian), Stereo, 48.000 kHz
I think you have to convert your audio portion to be 48kHz.
If when you scrub through your material in FC you can hear audio, but you get a beeping sound when simply playing back, then I'm pretty sure this is the issue. There would be a red bar on the top of the timeline for affected clips when something needs rendering, which can include audio.