Take a phone call today, and the quality of the sound will be the same as it was a few decades ago: sometimes fuzzy, sometimes muffled, with a tinny, robotic characteristic to it.

But a few short years from now, you're going to notice a big difference in the quality of your calls. That's because engineers are working on shifting the country's telephone infrastructure from copper wiring — the old technology that dates back to the days of Alexander Graham Bell — to fiber optic cables that can support a lot more traffic.

"More traffic" doesn't just mean more calls. It means those calls can be packed with more data, allowing for richer sounds. The traditional phone call uses audio frequencies ranging from 300 hertz to 3.4 kilohertz (kHz). The HD voice network, or HDN, is expected to allow audio frequencies as high as 7 kHz or more. For the end user, the experience will be akin to upgrading from ordinary TV to HDTV.

Daniel Berninger is a network engineer who helped design Voice-over-IP (VoIP) in the 1990s — the technology behind Skype, Google Voice and Vonage. His latest project is to transition the country's phone infrastructure to support all-HD calls. This process is already happening as telecom operators make the switch from copper to fiber; HD voice will simply become another application riding atop those pipes.

Berninger says he's in the midst of a pilot program involving all the major phone carriers, signing up individual phone numbers as test subjects for this HD-enabled future. Berninger has already gotten between 400,000 and 500,000 volunteers. By the end of next year, he anticipates that figure to rise to 4 million — and perhaps to 40 million the year after that.

There's a twist to this story, however. As we've discussed before, the transition to fiber also means a transition away from the old rules that used to govern the telephone network. Fiber, IP-based phone calls and HD voice are more lightly regulated when they're regulated at all, meaning that the government is going to consider what new rules, if any, might need to be written for this future platform.

The Federal Communications Commission can impose certain obligations on companies if they connect to or use telephone numbers. Berninger said that while he's fine with that approach, the HD voice network will likely exceed the expectations set by the old regulations policing the traditional phone network.

"They'll impose [cooperation with law enforcement], they'll impose disability access," said Berninger. "There'll be the checklist. But we, as the operators of HDN, will make [telephony] transparent and make it better. HDN will have HD 911. We will have text-to-911. It's in our interest in terms of attracting users —we're actually competing with the [public switched telephone network]."

For a taste of the difference in sound quality, PC Magazine ran some independent tests. Here are their samples: