Voice over IP (VoIP) is an emerging technology where voice is transmitted over packetized data networks instead of the traditional public switched telephone networks. The effective functioning of a VoIP system depends upon the quality of coding/decoding scheme, and on the networkÂ’s performance in transmitting the voice packets. Traditional measures of speech coder quality and network performance employ voice samples from normal talkers and it is unclear what impact abnormal voice samples will have on the performance of a VoIP system. The objective of this paper is to investigate the influence of speech samples from talkers who have a form of common voice disorders on the performance of three speech coders typically used in VoIP systems. Our results show that there is a significant difference in the performance of low bit rate speech coders with disordered speech samples, and that the packet loss affects certain coders more than the others.