to the passage below and then answer the question afterwards in the same language as the passage: Passage: GSM has used a variety of voice codecs to squeeze 3.1 kHz audio into between 7 and 13 kbit/s. Originally, two codecs, named after the types of data channel they were allocated, were used, called Half Rate (6.5 kbit/s) and Full Rate (13 kbit/s). These used a system based on linear predictive coding (LPC). In addition to being efficient with bitrates, these codecs also made it easier to identify more important parts of the audio, allowing the air interface layer to prioritize and better protect these parts of the signal. GSM was further enhanced in 1997 with the enhanced full rate (REF) codec, a 12.2 kbit/s codec that uses a full-rate channel. Lastly, with the robust development of EFTS, UMR was re-rowned into a variable-rate codec called AMR, which is called narrow-band (6.5 kbit/s) and full-rate (13 kbit/s). Àwọn wọ̀nyí lo ètò tí ó
láàárín 7 sí 13