It is well known that the quality of real-time applications, like VoIP, in wireless networks suffers great degradation due to the signal instability in mobile environments. In this paper the quality of VoIP applications on WiFi networks is evaluated using an emulation system with variation of the test environment following the Rayleigh distribution. With this system it is possible to maintain control of the environment and modify it, emulating real situations of WiFi networks in obstructed places.