Wideband, or the so-called high-definition voice is a good thing, as it allows for superior clarity and best audio experience in VoIP and calling. It doubles both the sound spectrum width, and the sampling rate, so voices come out exceptionally loud and clear, with a fraction of the bandwidth needed by the traditional solution.
Cupertino said at the announcement that 20 carriers will be supporting this feature when the iPhone 5 appears on their network, so this must be the best phoning device Apple has ever made.
The noise-cancellation is also aided by the three microphones, situated strategically front, back and bottom forming a beam to filter the background noise, and leave only that sweet HD voice sound in your ears. Orange is one of the carriers that has touted its HD voice support for a while now, so have a look at one of their old promo videos below to gauge what's in store with the iPhone 5.