poor sound quality in Storyline

Hi, 

I'm not happy about the sound quality in Storyline. Even with the publish quality settings at maximum, I'm getting a tinny sound. 

Could this have something to do with the mp3s I import into storyline? I use 320 kbps 44000 Hz  32-bit stereo mp3 recordings. The voice-over is pretty crisp, studio recorded.

Would it help to pre-convert all of the audio to some other setting? If so, which setting?

I can't pre-convert to the odd settings Storyline uses. These seems to be non-standard: 160 kbps 22050 Hz 32-bit mono mp3. With a 22050 Hz sample rate, the max bit rate should be 48 kbps. According to Adobe Audition, anyway. 

At any rate, the recordings do sound as though they are converted to 48 kbps.

Thanks for any help!

Ayoub