All the Unity prompts are, by default, recorded in 711(uLaw) at 8 Kb/sec (8 KHz, 8 bit mono). We also have a G729 set but there aren't too many recording applications out there that will have support for this. If you're going to prerecord your call handler greetings (I assume for audio text applications? or do you mean for subscriber greetings?) I would do it in this 711 format and roll with it.
The volume target level is -26dB and you're going to want to get as close to that as you can (fancy apps like CoolEdit will show you roughly what it is but, of course, this varies quite a bit). You can relevel your greetings afer you install Unity using the SetVolume application that ships with 3.1(3) and is also available on AnswerMonkey.net. You don't want to adjust too far, however, or you'll get distortion so try to get near -26 dB.
If you are importing call handlers for an audio text application, you can use the BulkHandler Create tool on AnswerMonkey.net to slurp in the handler info including the greetings, from a CSV file definition. You might want to read through the help file out there real quick so you can plan your file naming convention and get a CSV file worked up ahead of time.
Jeff Lindborg
Unity Technical Lead/Answer Monkey
Cisco Systems
lindborg@cisco.com
http://www.AnswerMonkey.net (new page for Unity support tools and scripts)