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VoIP over Wireless-LAN (VoWLAN) is gaining importance due to its excellent potential in wireless voice communication. With the rapid deployment of WLANs, there is a growing demand for WLANs to support voice applications. In this research paper we present simulation results by enabling the Speech Activity Detection (SAD) for seven codecs, i.e. G.711, G.723.1, G.729, G.726 (ADPCM), G.728 (LD-CEPT), G.729 (CS-ACELP), and GSM under similar load conditions for interactive Voice over WLAN system on the IEEE 802.11 wireless LAN standard. Additionally, results have also been obtained by disabling Speech Activity Detection and both sets of results have been compared. The primary metric used in the comparison is packet end-to-end delay. From our results we conclude that the use of the Speech Activity Detection significantly improves the Average Packet end-to-end delay and slightly improves the Average Packet Delay variation for all of the aforementioned vocoders. The G.723.1 vocoder provides the least end-to-end delay and packet delay variation under both conditions, i.e. with enabled and disabled SAD. With enabled SAD, the average end-to-end delay improves by approximately 58% for our experiments.