The performance of 2.4kbps speech codec is poorer than 4.8kbps and better than 1.2kbps. So in the future, the emphasis of low rate speech codec research is the 2.4kbps speech codec.

• 4kbps编解码器的语音有较高的可懂度，但音质处于4.；8kbps编解码器和1