Apple's iPhone 5 supports wideband audio — commonly known by many carriers as HD voice — which provides a higher-fidelity call quality than subscribers are typically used to. The company says that it's got 20 carrier partners ready to deliver HD voice at device launch, thought it hasn't named them.

The technology has been around for many years and has been deployed by a handful of carriers around the world, but a lack of supported devices has prevented it from taking off — an iPhone, which will undoubtedly sell tens of millions of units, could be just the catalyst that it needed to gain widespread acceptance.