HD audio
HD sound produces much more natural-sounding speech than the sound you get with conventional phone calls. It picks up tones of voice and nuances, making conversation more fluid. You might also encounter the terms wideband audio and HD sound describing the same advantage. They all utilize at least double the frequency range compared to narrowband telephony, from 50 Hz to 7 kHz or higher instead of only 300 Hz to 3,4 kHz.