It sounds like U.S. carriers won’t (yet) be able to take advantage of the iPhone 5‘s wideband audio feature. Verizon and AT&T were immediately ruled out after the feature was announced on Wednesday because neither supports HD voice, leaving Sprint as the last remaining hope. Unfortunately, the carrier’s CDMA 1x protocol conflicts with what the iPhone 5 supports. Boo.
Most carriers around the world do support HD voice, but largely using WCDMA networks; Apple said 20 carriers across the globe would support the feature, just not the U.S. it seems. It’s a big tease, and unusual for a flagship device bred in the U.S. to come without support for such a big feature. I guess we’ll have to wait until carriers and Apple get on the same compatibility page before iPhone owners can enjoy better sounding voice calls.