Voxware provides high-quality sound using low- to mid-range bit rates.
It comes with a variety of mono and stereo audio formats to choose from depending on your network bandwidth.
It is also suitable for encoding mono voice-only content at extremely low bit-rates.
MetaVoice works far FAR better than
mp3 and even WMA at very low bit rates. You can get very good speech quality at 2kbit/sec! (Note I said "bits" not "bytes" - you can't touch that with
mp3.)
It'll do soundtrack noises pretty well too, although it can get muddy if there's too much going on.
Using the MetaSound
codec and upping the bit rate to a whopping 8 or 16kbit/sec will fix this.
The best part is there are no restrictions on the Voxware
codecs - you can use'em in pretty much anything and they'll play.
MP4 Converter
0.64 MB 
$ 10000