HD Voice
(Wideband Audio)
Clearer sound for voice calls.
Traditional phone audio only transmits a narrow range of audio frequencies. This range is just enough for speech to be understood in most circumstances, but does not sound very clear.
Wideband audio - usually branded "HD Voice" - transmits a much wider range of audio frequencies. It generally uses more advanced digital compression techniques to capture more accurate, nuanced audio using the same amount of data, but may also use more data to deliver even better-quality audio.