I have been trying to stretch into sending voice messages over the net to another classroom. I can hear them fine but on their side we come out as garble garble. Sound set to mike. I know about problems with traffic over the net. All the connections seem fine.
Phone lines work ok for regular internet surfing.
That's no indicator of audio packets. No Firewalls except a porn filter at the server. A different audio program. Without knowing both machines processor and RAM config's. as well as the modem speed you can't assume that because you can hear them, but they can't hear you, the fault lies in your machine. Here's a puzzle to ponder.