Compared to video, audio handling in Flash Lite is generally simpler and similar to desktop Flash player. The conversion tools listed with video also encode audio streams and can be used for that purpose. Note that audio can usually be highly optimized for mobile use as the devices very rarely have more than one speaker and usually are not on the level of desktop systems in their sound reproduction.
You can check the audio capabilities of Nokia devices from Device Specifications at Forum Nokia. Select the correct device and find the Audio Formats heading, which lists all the supported audio formats by extension.
For more information about Flash Lite audio support, see the following documents:
Sound for Nokia S60 and Series 40 Devices at Forum Nokia
Optimizing Digital Audio for Flash Lite at Adobe Developer Connection