g729 bandwitdh & 40 simultaneaous calls

Hello

My understanding is G729 requires 23kbs of bw (8k voice, 15kbs overhead from protocols)

I have a box speaking to another one, in sip / g729. When I have 40 calls concurrent, I see through iftop an average usage of 700kbs max - ie 17-18kbs per call. Voice quality seems alright.

How can the bw per call decrease to that extent ?

Rgds,

J.

What protocol are you using ? sip or iax ?

Ian

sip - no iax