Lots of references get made these days to HD voice, and it can be a bit confusing to pin down a good definition for what, exactly, this technology is and what it can do. Part of the confusion is because ‘high def’ is a somewhat subjective concept. Just how good does audio quality have to be before it is considered HD?

A first step toward understanding HD voice is to refer to instead a more technical term, wideband audio. This is a better title because it makes reference to the technology needed to deliver high-quality audio—sound that’s much clearer than any telecommunication experienced before.

A Wikipedia entry notes that wideband audio “extends the frequency range of sound traveling over telephone lines, resulting in higher quality voice transmission.”

Also, traditional or ‘narrowband’ telephone calls were connected using audio frequencies ranging from 300 to 2400 hertz. That’s pretty limited, considering that human voice quality can be as high 14,000 hertz. Wideband audio gets much closer to that range, topping out at around 7000 hertz.

Technically, wideband audio entered the scene in the late 1980s, when the International Telecommunication Union (ITU) introduced G.722, a standardized version of the technology. However, traditional phone networks and telephony/audio devices were unable to accommodate wideband audio, so its use was quite limited until newer transmission and broadcast technologies (notably, voice over internet protocol) entered the scene during the past decade or so. 

Today, HD voice is being used to offer a better audio experience for VoIP calling.

HD voice has quite a few advantages over traditional narrowband audio. Communication misunderstandings are greatly diminished or eliminated. People speaking with one another have an easier time distinguishing between confusing sounds and understanding speakers with unfamiliar accents. This technology also makes communication easier when people speak softly, or when they speak at the same time.

As HD voice technology developed and became more widely used over the past ten years or so, it drove innovation among handset manufacturers and telecommunications carriers. It is now making inroads into mobile telephony as well.