Get ready for high-def voice

It will be years before it's pervasive, but preparing now will help

High-definition voice -- a rarity in today's business networks -- is becoming more common, so it makes sense for corporate telephony executives to figure out now how they will make the transition, experts say.

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 telepresence 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.

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High-definition voice -- a rarity in today's business networks -- is becoming more common, so it makes sense for corporate telephony executives to figure out now how they will make the transition, experts say.

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 telepresence 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.

Click to see: Diagram of an HD voice network

"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.

HD voice generates frequencies at the high end of human speech that toll-quality voice cuts off. In practical terms this means being able to hear the difference between words like "pig" and "fig" without asking whether that's a p as in Peter or an f as in Frankenstein.

Wideband voice pushes up the top frequency range covered by the voice coder-decoders (codec) from about 4 kHz to something higher, typically 7 kHz, but it can go even higher to 14 kHz or 20 kHz. One consequence of this wider band is the need to sample speech more times per second in order to capture more of its subtleties. Rather than 8,000 times per second, sampling jumps to 48,000 times per second.

That means the VoIP phones supporting HD need more powerful processing and memory, both of which cost more, but with Moore's Law applied to the phones, the cost differential is narrowing. For example, Polycom's SoundPoint IP 501 phone with Power over Ethernet (PoE) and three lines but with no wideband support costs $295. A roughly comparable SoundPoint IP 550 with PoE, four lines and HD support costs $369.

As Polycom introduces HD phone models, it is phasing out the equivalent narrowband phone, so eventually all its line will support wideband and remain backward compatible with narrowband, Rodman says.

Because the endpoints and the networks between the endpoints must both support HD voice in order for it to work, most wideband deployments are within corporations, not between them, says William Bumbernick, CEO of Alteva, hosted VoIP provider. "The ability to call a different company on a different carrier and completing an HD call is becoming more and more expected," he says, but "today, the chances are still pretty slim that that will happen."