if go to this page
http://eng.iaudio.com/ and press download button and look at the firmware upgrades for the G3 and the U2 you see this:
- ADPCM wave format * is supported.
- WAVE 8kHz, 11kHz, 16kHz, 32kHz are added to recording quality
# What is ADPCM format?
It is a file format that is saved as wav file which can be played with Windows.
Compressibility is about 4:1. It is lower than MP3 format, but sound quality is similar.
Recording frequency range is 8KHz~44.1KHz.
Recording with low requency would allow more capacity and battery life.
looks intresting, anyone have experience with it?