Google Voice

I am using Gizmo5 with Google Voice so I can make free phone calls from PC to landline. With the first two calls from PC to landline I had perfect reception; however, the other party said my voice was garbled and hard to understand. I was using wi-fi with my notebook and a headset for these calls. I will try again in the future but unless I can get better call quality I don't think it will be very usable for calls to a landline; however, the main purpose for me is to use it as an answering machine.