UPDATE / Jan 23, 2014: 2degrees has followed Vodafone in launching HD Voice - a technology that provides uncanny clarity compared to traditional cellphone audio.
There's no extra cost; it will just kick in if you're using an HD Voice-compatible handset (listed here).
The catches: the person you're calling must also have an HD Voice-capable phone, and you can only HD call another 2degrees customers - 2degrees' and Vodafone's HD Voice systems are not cross-compatible.
A spokeswoman for Telecom earleir told NBR, "We’re pleased with the current quality of our voice network, which is performing very well - but we are constantly looking ahead to new technologies and features. We have been reviewing HD voice technology and may look at bringing it to market in the future."
Customer Jonathan Mosen tells NBR he's used HD Voice on Vodafone and 2degrees and it's "Equally good on both."
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Vodafone launches HD Voice - early callers' verdict
Nov 7, 2013: Vodafone launched HD Voice today. It says the new service lets you make a voice call with crystal clear clarity.
Auckland man Paul Brislen - usually seen on this site moaning about one thing or another - was a pre-launch triallist, and says it's a knockout.
The audio is as clear as advertised; he could even hear a caller writing on a pad as they talked. It was like talking to someone in the next room.
"I think we all got used to awful sound quality on mobiles and to have proper audio is great," he told NBR during an HD Voice phone call.
Vodafone says around 250,000 can use HD Voice.
That's the number of people who have an HD Voice-compatible smartphone - and if you do, it's free.
The following phones are compatible (although you might have to update to the most recent version of your handset's operating system software in some cases):
Mr Brislen says the HD Audio technology deployed by Vodafone can be used cross-network.
However, it looks like it will be a while before it's adopted by rivals.
A spokeswoman for Telecom told NBR, "We’re pleased with the current quality of our voice network, which is performing very well - but we are constantly looking ahead to new technologies and features. We have been reviewing HD voice technology and may look at bringing it to market in the future." 2degrees could not immediately comment in detail.
It doesn't seem like the technology is a winner every time. During NBR's call with Mr Brislen, the Tuanz boss sounded more in-your-ear than ever before - although the difference is perhaps best described as being akin to moving from AM to FM radio than the caller sounding as if they're standing next to you (as Vodafone bills it).
NBR was impressed. But Mr Brislen said NBR (using an iPhone 5s) sounded more or less the same as previous conversations.
NBR also fielded a call from another pre-launch user, journalist Bill Bennett, who has been using HD Voice for interviews.
Mr Bennett describes the difference between normal cellphone calls and HD Voice as like moving from AM radio to CD. He says sibilants (thinks "s and "f") are now much more clear. There's now much less asking people to spell out their name.
NBR agrees. If still not 100% natural sounding, HD Voice is amazingly clear. Listening to it the first time is spooky. At it's best, it is as if the caller is standing next to you. At it's worst, it can sound very clear, but also a touch synthetic and harsh. One caller, Matthew Hooton, even asked NBR if it was possible to turn off HD Voice.
Vodafone launched 4G as data-only, continuing to use its 3G and 2.5G networks for all voice calls.
HD Voice calls are routed over 3G, but unlike "standard definition" calls over 3G they double the digital samples rate from 8,000 per second to 16,000 per second.
And Vodafone says a normal cellphone call has frequencies between 300 Hz and 3.4kHz. HD Voice increases the upper limit to 7 kHz or higher, more closely matches the frequencies used by normal human speech.
If you polled random users on any network, better coverage outside of main centres, and in those annoying urban nooks and crannies, would probably top their wish list of new network features - followed by bigger mobile data caps.
I'd never particularly thought of voice fidelity as a problem that needed solving - at least at times when I've had decent 3G signal strength. But when you hear HD Voice, it's pretty impressive. I'm still not sure if I'd pay extra for it - but you don't have to; it's free.
I've been making HD Voice calls from my iPhone 5s in NBR's office, which is at a downtown Auckland location where call quality is always pretty good anyway. It'll be interesting to try it tonight from home, where reception is very average, and to see how that HD quality holds up.
Lastly, if voice quality is important to you, and you're an iPhone user outside of the Vodafone camp, I recommend you also try FaceTime Audio. Unlike the better-known FaceTime Video, it works over wi-fi or cellular, and it's a marked quality improvement over a regular mobile phone call. FaceTime Audio is a hidden gem. Just keep an eye on that data cap.