HD Voice , which improves voice-calling clarity , is coming to more U.S. networks . Feature expands frequency range of sound transmitted by phones . AT & T confirmed its plans to add HD Voice later this year . Comment:
HD Voice , which improves voice-calling clarity , is coming to more U.S. networks . Feature expands frequency range of sound transmitted by phones . AT & T confirmed its plans to add HD Voice later this year . T-Mobile , Verizon and Sprint are also looking at the new technology .