first 2-3 seconds of the greeting not being heard

Hi,

Why is the first 2-3 seconds of the message not being heard ??

After the call connects, I cannot hear the first 2-3 seconds of the message. I can hear the balance message.

As suggested in another post, I can insert a 3 seconds blank audio in the wav file and then start the main greeting.

But I want to understand what is causing the first 2-3 seconds of the message not being heard.

Any ideas ??

Thx
Vai