Adaptive Multi-Rate Codec

A family of audio codecs used in mobile telephony to encode voice for transmission. AMR-NB (narrowband) operates at 300-3,400 Hz with bit rates from 4.75-12.2 kbps, while AMR-WB (wideband, also called HD Voice) extends to 50-7,000 Hz at 6.6-23.85 kbps. AMR-WB is adopted by 3GPP standards for implementing wideband cellular audio, providing significantly better speech recognition and quality for people with hearing loss compared to AMR-NB.