Perceived degradation effects in packet speech systems

A packet speech system´s sound quality is degraded when packets do not arrive at their destination in a timely fashion. This can happen when packets are lost in a network or when network delay is excessive. Simulation results are reported which measure the effects of such losses and delays on sound quality and intelligibility. Thirty human subjects were asked to listen to the output of a simulated packet speech system in which some packets are missing. Sound quality and intelligibility were measured as a function of packet loss and packet length.