Codecs & Voice Quality
HD Voice
By Myroslav Orshak · operates licensed carrier infrastructure · Updated September 2026
HD voice is wideband calling — it carries roughly double the range of sound a traditional phone call does, which is why some calls sound like the person is in the room and others sound like a telephone.
How it works
Traditional phone calls carry frequencies from about 300 to 3,400 hertz, a range chosen in the era of copper wires for being just enough to make speech intelligible. HD voice widens that to roughly 50 to 7,000 hertz or beyond, using codecs such as G.722 or Opus.
What you gain is the parts of speech that narrowband throws away: the low end that gives a voice its body, and the high end that separates consonants. That is why f and s sound alike on an ordinary call, and why spelling a name or reading out a reference number is so much easier on a wideband one.
Why it matters
It reduces listening effort, which matters most over a long day. On a narrowband call your brain is quietly reconstructing missing information, and that is tiring in a way people do not attribute to the phone. Teams that spend hours on calls notice the difference in fatigue before they notice it in sound.
The frustrating part is that both ends must support it. Two IP phones on the same modern system get HD voice automatically; the moment either side is an ordinary landline or an older handset, the call drops back to narrowband and there is nothing to configure. This is why internal calls can sound noticeably better than calls to customers, which confuses people who assume something is broken.
Traditional narrowband carries about 300–3,400 Hz. Wideband via G.722 carries roughly 50–7,000 Hz, and Opus extends further still. The gain is concentrated exactly where consonants live, which is why names and reference numbers become easier to hear.
Related terms
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Compare business phone systems →Frequently asked questions
Do I need to turn HD voice on?
Rarely. Modern phones and providers negotiate the best codec both ends support automatically. If calls sound narrowband when they should not, check that the wideband codec is not disabled in your phone system's codec list, which occasionally happens when someone restricts codecs to fix a fax problem.
Why do some calls sound better than others?
Because both ends must support wideband. Internal calls between two modern IP phones get it; calls to a cell phone or a traditional landline usually do not, and the whole call falls back to narrowband. Nothing is broken — you are hearing the limit of the other end.
Does HD voice use more bandwidth?
Somewhat, though not enough to plan around. A wideband call uses more data than a narrowband one, and both are small compared with any modern business connection. Steadiness of the connection matters far more than the extra capacity.
Is HD voice the same as a higher MOS score?
Related but not the same. Wideband codecs can score above the narrowband ceiling on scales that account for it, but MOS mainly measures impairment from delay, jitter and loss. A wideband call on a bad connection still sounds bad.