The signal distortion on encoding and decoding of EVRC-B is much higher than G711. For a back to back EVRC-B test, the signal is undergoing these distortion during the process. In the case of G711 -- transmeida server -- EVRC-B test, there is only one encoding or decoding on the EVRC-B side. Hence the overall signal distortion is smaller, resulting in a better PESQ.