A scheme named index assignment-based channel coding (IACC) has been developed for resilience of speech/audio codecs against the bit errors commonly experienced in wireless channels. Although IACC is a type of joint source channel coding, it does not intervene with the source codec design. The proposed scheme takes into account source characteristics and adjusts the amount of coding according to the sensitivity of different values of the source parameters. It is shown that source characteristics play an important role in the performance of IACC. The performance of IACC has been evaluated by applying it to parameters generated by adaptive multi-rate wideband (AMR-WB+) audio codec. A method for perceptual training of IACC codes is also proposed. The results demonstrate that the performance of IACC and IACC concatenated with convolutional coding can be superior to that of conventional convolutional coding at high and moderate bit error rates, respectively.