How much bandwith do I need?

I work from home and we use a VOIP program and also Microsoft Lync.
When my wife is running Netlflix my audio cuts in and out. She has no issues streaming.

I have no issues running Netflix HD on 2 devices.
I am getting over 20 Mbps download speed from Time Warner.

Any idea why my audio programs have issues but Netflix doesn't?
Do I need to bump up to 30 Mbps?