There are so many things that can affect call quality. The #1 thing being your home network and bandwidth management. Even myself, who has been doing this stuff literally for more than 30 years, have home network issues sometimes. Usually it's a balance between available bandwidth and QOS in the system. Some people get around this if they know how to do QOS. But then you have to ensure you have a quality router. Other issues usually result because of port issues. Some people put their voip adapter into the DMZ. Some try port forwarding. Bottom line is: No two home networks are exactly the same, when you add in their local Internet service.

The best thing that improved all of my voip calls, was my cable provider now offering me 30mb down and 5mb up bandwidth. I've turned off ALL QOS because I have more than enough bandwidth to have a phone call happening while downloading or streaming.

Voip itself is a very simple concept. Your local phone company has been using a form of Voip for ALL of your phone calls that leave your town and go to any other location. They've been doing this for more than 35 years. But their network is/was dedicated to just THEIR voice packets. It isn't competing with people checking email, streaming video/music, surfing, etc... That's why individual consumer voip use can be hit or miss. It depends on YOUR ISP. Depends on your local internet service/connections/bandwidth. Depends on your home network, how it's setup, bandwidth management, and security/port setup.