Some steps the maximum benefit from HD voice.

1. Start by knowing just what HD voice is. Despite its reputation for realistic-sounding audio, HD voice doesn't deliver from speaker to listener the full spectrum of sounds audible in a real-life conversation. It does, however, transmit more than double the range of audio frequencies that traditional phone calls do. PSTN connections, sampling voice audio 8,000 times per second, transmit frequencies from roughly 300 Hz to 3,400 Hz, a range of just over 3 KHz. HD voice technology, sampling the audio 16,000 times per second, can transmit frequencies from around 50 Hz to 7,000 Hz, a range of almost 7 KHz. In concrete terms, that means HD calls can carry sounds a full two octaves lower, as well as sounds significantly higher, than those in conventional calls.

The difference is important because humans can detect frequencies ranging from 20 Hz to 20,000 Hz (20 KHz), and human speech typically spans a 10-KHz to 12-KHz band within that range. Thus a PSTN call delivers sounds representing only a fraction of the range one would hear in a live conversation — the rest is deliberately filtered out. And HD voice, though still not transmitting all audible frequencies, delivers enough of the ones relevant to human speech that many listeners say it seems like the speaker is in the same room.

2. Understand the real-world limitations of conventional PSTN voice. Understanding how much easier HD makes communicating by phone requires first understanding how hard traditional voice technology makes it. That's difficult to grasp because we're so accustomed to the limitations of the PSTN that we hardly notice them. But they're very real. To start with, cutting off so many high and low sounds makes distinguishing between s and f, or other similar sounds, a major challenge. Likewise, many individuals have voices that are significantly higher- or lower-pitched than others'. Thus in conventional conference calls it's often difficult to know who is speaking. It's similarly hard to understand people with different accents — an increasingly important consideration when even small businesses are often global operations. It's also easy to miss subtle verbal cues that come through in live conversations.

Such limitations impose significant penalties on call participants. For one thing, they force listeners to make extra efforts to understand what is being said and who is saying it, by interpolating or simply guessing. That can be mentally exhausting, particularly during long conference calls. And if participants have trouble discerning, for example, whether a key number was $15 million or $50 million, or which executive was in favor of a key proposal, it can even be disturbing.

3. Understand what HD voice will and won't do for you. The main benefits of HD voice lie simply in eliminating such penalties. Long calls, especially conference calls with multiple speakers with different accents, become less tiring and thus more productive. Participants are able to spend less time calling back afterward to clarify what various speakers said, or worrying that they got it wrong. Other benefits are less tangible. For example, because it lets so many more verbal nuances come through, HD voice may improve a company's rapport and image with whatever customers are involved in such calls. On the other hand, it definitely won't provide the kind of clear-cut ROI, such as measurable savings on long-distance charges, that moving to VoIP transport, for example, does.

4. Get HD-capable phones, not HD-compatible ones. Jeff Rodman, Polycom co-founder and voice division CTO, argues that IP phones with HD codecs such as the ITU-standardized G.722 may not necessarily provide true HD voice quality. That's because it takes more than a codec to deliver the full range of sound that the codecs can theoretically transmit. For example, HD-capable microphones and speakers are also necessary, as well as careful acoustic design. Polycom and snom have been particularly aggressive about building IP desk phones that take full advantage of HD voice, and AudioCodes is moving in the same direction. Softphones, the client software programs that allow users to make VoIP calls through headset-equipped PCs, can also provide HD capability.

5. Make sure your IP PBX is HD-compatible. For HD phones to work, whatever IP PBX they are connected to has to recognize the codecs they incorporate. Most IP PBXes these days are G.722-aware, but many IP phones contain other codecs in addition to the basic ITU standard. Making an IP PBX compatible with a given codec is a software upgrade, though compatibility testing is always necessary. Either way, make sure the different types of equipment you're using or planning to buy work together.

6. Make sure your network equipment can handle it. Polycom's Rodman also noted that in certain cases wideband codecs will increase the bandwidth requirements of phone calls. While the G.722 codec requires the same bandwidth per call as the narrowband G.711, some existing VoIP setups using high-compression codecs may be designed to use even less bandwidth. In such cases, moving to HD voice may not only increase bandwidth requirements, but also put a strain on queues, buffers and other elements of your LAN and WAN equipment.

7. Analyze your telecom connections and service. HD phones aren't much help if the connection between them can't support HD calls. But that's exactly what happens whenever a call travels over the PSTN for even a portion of its journey — the entire call becomes narrowband. There's not much you can do about it when you're making or receiving calls to or from outside companies or individuals. You have much more control, though, for calls between branches of your own company. Choosing a provider that offers end-to-end SIP (session initiation protocol) connections, for example, will also let you have end-to-end HD voice. And it will do so even if you have different types of HD phones or softphones at different locations. When it first sets up a call, SIP checks the endpoints, in this case the IP phones, to find out what codecs they have in common. It then transmits the call using the protocol that will provide the highest-quality connection.

8. Consider HD-capable hosted VoIP. Like IP PBX vendors, hosted IP PBX providers are seeing the light when it comes to HD voice. Companies such as Alteva, Apptix, FreedomIQ, IP5280 and LightEdge Solutions, for example, offer services that can use HD-capable phones from Polycom. And snom has introduced a number of phones incorporating the HD technology it calls klarVOICE wideband audio, which it is targeting at so-called standards-based (i.e. SIP-based) hosted VoIP services, among other applications.

9. Use an HD voice-capable conferencing service. As noted, conference calls are one place where you want to make sure everyone can hear everyone else as clearly as possible. Most commercial conferencing services, however, focus almost exclusively on PSTN connectivity. A Citrix Online service called HiDef Conferencing, formerly Vapps, similarly allows callers to dial in from the PSTN. But because it is integrated with Skype, any or all participants can alternatively call in on the Internet phone service. Those who do will hear at least each other in Skype's full HD glory. Similarly, a number of Web conferencing services offer a VoIP option with HD capability for the audio component of their online meetings. And VoIP conferencing service ZipDX, which supports HD (which it calls wideband) voice conferencing with Polycom phones, recently announced the integration of its service with snom klarVOICE phones as well.

10. Be aware — or beware — of background noise. Remember that HD voice connections transmit a lot of sounds that PSTN calls don't. Listeners will hear every rustle of a paper, every click of a keyboard, every conversation in the hallway and every sound from the next cubicle. One soon learns that "potato chips have different ranges of crunches," noted Cailin Pitcher, senior marketing manager for Citrix Online.

11. Wait for the world to catch up to you. Even with HD equipment and SIP phone service, you may not have a lot of HD voice calls to start. The ones you do have will mainly be internal calls between branches. For outside calls, you'll be stuck with mostly non-HD connections for some time. That's because end-to-end HD calls across different service providers' networks require that the providers have interconnected IP voice networks, with no transit over the PSTN. And there won't be enough such interconnections to make external HD calls commonplace for years.

That doesn't mean you shouldn't go with HD right now if it otherwise makes sense. The phones you buy today will typically have a useful life of six to seven years, or longer. And they should (make sure of that, too) be firmware upgradeable for compatibility with new codecs as those come out. By that time, there will be a lot more interconnected provider VoIP networks, so even calls to and from outside customers or suppliers could be HD as well. In the meantime, your own internal communications will improve dramatically. That alone could make the investment worthwhile.