If they want to, IP PBX vendors can issue software upgrades to support better-quality voice calls, but upgrading handsets and getting service providers onboard with the technology is a more complex proposition that needs to be thought through, they say.

The benefits of HD or wideband voice include an easier understanding of what is being said and a more authentic reproduction of live speech, both of which are essential in immersive systems that generate the illusion that conference participants are seated across from each other in the same room, says Jerry Knight, CTO of Accessline, the audio services arm of video service provider Telanetix.

"Video perhaps is not as important as audio in creating that impression," Knight says. "Audio is at least as important."

The benefits of HD are not so obvious in voice-only uses. But the difference can be significant especially with speaker phones and when talking to people with strong accents, where every bit of clarity helps, says Polycom co-founder and CTO of its voice communication branch Jeff Rodman. "In these cases we need all the clues we can get," he says.

HD voice gives better quality than what used to be the premier telephony standard in the public-switched telephone network (PSTN) -- toll-quality voice.