asterisk users - Dec 2004 - Source/cause of echo delay (on internal stuff network)

Hi All,

This one has me stumped, but I've done quite a bit of debugging to
hopefully isolate it down enough. Basically, I hear an echo *delay* when I
do a 'echo' test (key- there's an annoying delay). Here's what I
have:

Asterisk 1.0.3 current as of Dec 7.
x100p (although, irrelevant in this case)
(2) Cisco 7940's with 7.3 firmware

All communications between asterisk and the phones are over SIP.

o If I call from phone to phone on the local network (100Mb switched), I
hear no echo delay- sounds great.
o If I disconnect the phone from the network, I can hear my voice in the
earpiece (obviously, no delay).
o If I check my voicemail off of the 7940 (talking directly to asterisk),
I hear no delay (just audio to the earpiece from the phone itself)
o If I do an echo test, I hear the delay. Here's the exerpt from my
extensions.conf file that does this:

  exten => 10,1,Playback(beep)           ; Let them know to start
  exten => 10,2,Echo                     ; Do the echo test
  exten => 10,3,Playback(demo-echodone)  ; Let them know it's over
  exten => 10,4,Hangup

I run the test, and I hear the echo delay. This is on a asterisk server
with a network latency of ~.2ms. The asterisk server is a P3-600 w/ no
activity on it (totally idle cpu).

* My question is this: The phone generates enough echo via the earpiece, I
don't really need to have asterisk send me my voice back to me. Is there a
way to do one of the following?

1) Tell asterisk to not send my voice back to me.
2) If there is no way to stop this, how do I get rid of the echo-delay?

Hopefully someone reading this will have some insight on what can be done.
It's bad enough where it's not usable.

Much thanks in advance,

-Eric