As part of the unveiling of HTC's Evo 4G LTE today, Sprint has also announced that it'll be flipping the switch on so-called HD voice service late this year. HD voice — which has been available on a few European networks for some time — promises higher-fidelity audio quality on phone calls. It's something we've been able to get through VoIP services like Skype for years, and the traditional landline and cellular phone networks are just starting to play catch-up.

Interestingly, Sprint won't be waiting for voice over LTE (VoLTE) to roll out HD voice. Instead, it'll be available on its 3G network in areas that have been upgraded to the so-called 1X Advanced standard, an evolution of CDMA that Sprint intends to deploy footprint-wide over the next several years as part of its Network Vision strategy. Though the Evo 4G LTE is the first announced HD voice device for the US market, the late 2012 guidance on HD voice network compatibility means that users will be waiting a while to try it out; that's probably okay, considering that both devices on phone calls must be compatible for the service to function. The company expects it be available across the entire product range within two years.

Verizon and MetroPCS are both likely to roll out VoLTE starting this year — and with it, HD voice compatibility. Whether they'll actually beat Sprint with a commercially operational HD voice market, though, remains to be seen.

Coincidentally, the deployment harks back to Sprint's famous "pin drop" commercials for its long-distance service in 1980s and 90s — and if HD voice service is as good as it claims to be, users should have no problem running the test themselves.