Half second of silence when answering call

[ncg]

When I receive a call from the PSTN (on BRI) on my extension (SIP) there seems to be half a second or so of silence at the other end, so if i say "He Fred" then Fred doesn't hear the greeting.

A sound engineer called, and he reckoned my voice faded in at the start of the call.

Might this be because i have too large an echotraining number in my zapata.conf?

Any other possible explanations?

Thanks!

Nigel.