does vokoscreen support downloading sound.i get only video

You mean recording audio ?
Yes it does support it. By default it might be deactivated. Go to the Audio/Sound tab and activate the checkbox right next to audio and choose the correct sound card. By default Netrunner Rolling uses the Pulse (Pulseaudio) Backend. So make sure that is checked and that the right card is checked next to it.

If you are unsure which card your mic is connected to you can try installing pavucontrol and start this to see live levels from your input devices. The naming of the device should be the same so you can easily check the device you want then in vokoscreen.

Hope that helps.