[Asterisk-Users] Codec audio quality comparisons?

[Scott Bussinger]

I've seen lots of comparisons between the various codecs with respect to
bandwidth requirements, but are there any comparisons with respect to
quality?

I'm currently using ulaw internally and gsm to connect to my ITSP, but
should I be using different codecs to get better sound? Could someone who's
played with all of them rank them in order of quality or point me to
somewhere that's got a comprehensive comparison?

For example, is it worth paying money for g.729 licenses for my users?
Should I be hounding my ITSP to support SPEEX? Is g.711 absolutely the best
possible sound given the bandwidth it uses?

Just to be clear, I'm calling highest quality the least noise and hiss,
fewest sound anomolies, least echo effects, and least delay.

Thanks!