1) The ITU approved this way back in 1987.
2) The voice range is increased from 300Hz-3.4KHz to 150Hz to 7KHz.
3) The range your ear can hear is about 20Hz to 20KHz.
4) The human voice ranges from 80Hz to 14KHz.
5) The bitrate is (max) 64bps at 14bits.
6) A CD uses (max) 44KHz at 16-bit at 1.4mbps