Should You Heed

By Andrew Garcia  |  Posted 2007-09-11 Print this article Print

the Call for HD Voice?"> High-definition voice over IP—as exemplified by Polycoms HD Voice technology—provides outstanding quality and clarity for calls within a companys borders and could be an important building block for a range of applications in the future. However, shortcomings of the Public Switched Telephone Network—and of the telecommunications industry in general—limit the current usefulness of the technology outside the corporate network. This became clear to me as I stood in Polycoms isolated demonstration booth at the Spring VON show in San Jose, Calif. I was immediately struck by the quality of the sounds produced by Polycoms SoundPoint IP 550 and IP 650 HD Voice phones. When compared with a toll-quality implementation side by side, the HD Voice transmissions were perceptibly richer, fuller and clearer.
A combination of technology and education helps address VOIP threats. Read more here.
High-definition VOIP gets its full sound in a few ways. First of all, high-definition VOIP uses wideband codecs between endpoints. Normal telecommunication samples a range of audio frequencies (from 300Hz to 3,400Hz) for transmission across the limited bandwidth afforded in the PSTN. Early-generation IP phones followed suit, as the codecs most frequently used with VOIP (such as g.711) were designed to meet but not beat the expectations for toll-quality voice. Polycoms HD Voice phones, on the other hand, can sample sound between 150Hz and 7,000Hz, and the sound is then transmitted via wideband codecs (in this case, g.722), which can support this wider range. Since the human voice starts at a base frequency of about 100Hz and extends up toward 8,000Hz, the improved sampling of the high-definition technology has a number of potential benefits. For example, users will expend less energy deciphering sounds—particularly easily confused consonants, such as the letters "f" and "s." This will lead to better overall comprehension and less fatigue for callers who spend hours a day on the phone. Deciphering foreign accents or dialects should take less effort as well, fostering improved international dialogue. Beyond the compression and encoding algorithms, high-definition VOIP requires some advanced engineering on the physical phone. Improved audio components and enhanced echo cancellation or noise suppression provide better sound quality (no matter what codec is used), but these features can also help avoid the rumble in the low frequencies or acoustic feedback at the higher frequencies that wideband codecs will open up. Page 2: Should You Heed the Call for HD Voice?

Andrew cut his teeth as a systems administrator at the University of California, learning the ins and outs of server migration, Windows desktop management, Unix and Novell administration. After a tour of duty as a team leader for PC Magazine's Labs, Andrew turned to system integration - providing network, server, and desktop consulting services for small businesses throughout the Bay Area. With eWEEK Labs since 2003, Andrew concentrates on wireless networking technologies while moonlighting with Microsoft Windows, mobile devices and management, and unified communications. He produces product reviews, technology analysis and opinion pieces for, eWEEK magazine, and the Labs' Release Notes blog. Follow Andrew on Twitter at andrewrgarcia, or reach him by email at

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