Speech encryption is becoming increasingly important as the increasing relevance of multimedia applications such as video conference and news broadcasting. However, multimedia encryption and decryption are often computationally demanding and unpractical for power-constrained devices and narrow bandwidth environments. To tackle this situation, two novel selective encryption schemes are presented for G.729 speech in this paper. In the proposed schemes, speech bitstreams are partitioned into two parts based on bit sensitivity, i.e., one is encrypted by a high degree of encryption, and the other is encrypted by a lesser degree. To test the schemes, we introduce two chaotic maps, i.e., cat map and logistic map, and give contrast experiments addressed in signal inspection and objective distortion measure. Additionally, we discuss the two schemes' cryptanalysis and computational complexity. The results demonstrate the effectiveness of our selective encryption schemes for power-constrained devices and narrow bandwidth environments.