Comparison of two speech communication codecs for transmitting voice/speech over Zigbee This paper compares SPEEX and OPUS speech codecs for wireless sensor networks (WSN) based speech/voice transmission between two wireless nodes. The characteristics and parameters for both the codecs has been discussed below with their Graphs (Quality versus Bit-rate) based on the listening test conducted by Google. The OPUS codec represents itself the best among other codecs for the transmission of voice over wireless sensor network (WSN) in the current scenario and in coming future.