T-Mobile USA is the first carrier to launch HD voice service in the United States.

quality with significantly reduced background noise.
T-Mobile HD Voice leverages the Wideband Adaptive Multi-Rate (Wideband AMR) codec – a technology which accommodates an audio frequency range that’s twice as wide as a regular, narrowband cell phone call – as well as enhancements to the microphones and speaker systems in T-Mobile smartphones.
“T-Mobile is enriching the customer experience on its network with our nationwide launch of HD Voice. In addition, multiple third-party tests have shown that the experience on T-Mobile’s nationwide 4G network rivals major competitors’ LTE networks,” said Neville Ray, chief technology officer, T-Mobile USA. “This year, we’re stepping on the gas again. We are making continued coverage improvements and launching an advanced LTE network that will reach 100 million people by mid-year and 200 million people by end of year.”