Audio File Sizes
When creating audio files for an Audio Activity, you should try to keep your file sizes small. This is especially true if you're publishing your app to the Android Market -- each audio file will add to the size of your app, and the Android Market only permits apps up to a maximum size of 50 MB. (You should also consider that many devices have limited space for installing apps.)
For this reason, you will most likely want to avoid higher bit rates, as they will quickly use up your available space. For most apps a bit rate of 128 kbps or less will be required in order to fit more than a few tracks into a single app.
Note: Andromo currently limits the size of each uploaded audio track to 6 MB. If your audio files are too big, you will need to make them smaller (e.g. re-encode them at a lower bit rate), or host them on a web site and let the users stream them instead.