Vodafone touts HD voice technology

                                        HD VOICE: New service improves the audio quality of mobile calls.

Telecom will switch on its 4G network in parts of Auckland, Wellington and Christchurch tomorrow, joining Vodafone in offering faster mobile broadband speeds.

But a development with perhaps more immediate practical benefits for consumers occurred on Thursday, when Vodafone became the first of the three mobile operators to flick the switch on "HD voice", a technology that improves the audio quality of mobile phone calls.

Some phone users have described the quality of calls as being almost unnerving.

The average human voice ranges in frequency between 80 hertz and 14kHz, but mobile phone standards have limited calls to frequencies in the much narrower range of 300Hz to 3.4kHz.

Even then, sampling means only small "slices" of callers' speech make it across the airwaves.

Hence, mobile phone calls generally sound tinny.

Advances in mobile and compression technology have meant that, for several years, carriers have had the ability to provide much higher-quality voice calls.

The technology standard for HD voice was agreed by boffins at the International Telecommunications Union way back in 2003 and allowed for the capture of all frequencies between 50Hz and 7kHz.

Knowing better things were on the way, handset-makers have been incorporating better microphones and speakers as well as faster processors into their phones.

Now, Vodafone says 250,000 customers on its network own devices such as the iPhone 5, HTC One and Samsung Galaxy S4 that are able to support HD voice.

The "chicken and the egg" arrived on Thursday, when Vodafone switched on support for HD voice. It described the improvement in call quality as akin to switching from standard definition to HD TV.

2degrees said in 2011 that its network was "HD voice ready" and that it would switch the feature on "when customers asked for it". Telecom said then that it was watching the technology with interest.

Not much appears to have changed. Telecom spokesman Richard Llewellyn said yesterday that it was "pleased with the current high quality of its voice network", but it had been reviewing HD voice technology and might look at bringing it to market in the future.

2degrees was not aware of any progress, but it can only be a matter of time before both companies follow Vodafone's lead.

In the near term, HD voice could let mobile operators leapfrog the quality provided by landlines. If you are used to asking people to call you back on your landline so you can hear them better, the reverse could soon apply.

But internet telephony should do for landlines what HD voice is now doing for mobiles.

Telecom's Public Switched Technology Network (PSTN), which is used to deliver conventional phone calls, limits landline calls to a 64 kilobit channel.

That is pathetic considering customers signing up for ultrafast broadband can order a 100 megabit-per-second broadband connection to their home; that is a pipe more than a thousand times wider.

Even that 64kbps capacity is rarely fully-exploited in the cutthroat world of voice-call carriage.

There is no reason why mobile phone users shouldn't soon all be enjoying CD-quality sound and why landline callers shouldn't expect something even better.

Disappointingly, Telecom boss Simon Moutter has signalled that when it finally launches its delayed internet telephony product in a few months time it will be pretty much a straight replacement for its existing PSTN service with perhaps no more bells and whistles.

Many people might need to buy new handsets to get the benefit of a better service. But the biggest obstacle to clearer calls may be that phone users don't realise what are they have been missing, and have been demanding too little from their providers. Hopefully Vodafones launch of HD voice will start to change that.