Network packet loss is a common issue that VoIP (Voice over IP) applications need to take into account. In this study we simulate various levels of packet loss to examine its adverse effects on a novel speech codec called SYMPES, and compare the results with a number of well-known codecs, namely GSM-FR, G.711, Speex and iLBC. Although experiment results show that SYMPES and other non-predictive codecs react similarly under high packet loss conditions, they also indicate that SYMPES is relatively resistent to packet loss on the average.