Streaming feeds, getting video but no audio?

[Basil]

Spent an hour or so looking at streams, for example GB3KM. I get good video, but only a hum as audio. This is the same on other streams, I have yet to hear any audio. What can I be doing wrong? I do have a slow internet access as I am out in the sticks on old aluminium cabling, but I would have thought I'd still get audio? Help, fascinating things being shown, but no idea what they are talking about! Thanks.

EDIT, it's my external audio card lead, it's a M-Audio Delta with an external in / out box, the left channel is playing up. I have a new one somewhere but it's gone missing. On a USB headset now and audio is working. My apologies.

There is a lot of lag though, the audio is out of sync with the video by a couple of seconds.