It depends illiquid.
But you can work it out fairly easily. I believe most phones use much less than 64000 bps each way (more like 15,000bps so that you can just use them with dial modems and internet connections).
Even 64,000bps is much less than the 7,000,000 bps I get on my cable and 1,500,000 bps you might get on a poorer broadband connection. Thats 1-4% and wont affect your trading datastream.
You are more likely to have contention over processor load between trading apps (charting particularly) and the voice processor so if you had a very slow pc you might suffer from the interaction (press alt ctrl del to bring up the task manager and look at the cpu load of differnt processes).