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In this paper, we propose a hybrid energy saving mechanism (HESM) that combines power-saving mode (PSM) for real-time traffic with PSM for non real-time traffic, which is applicable to Voice over IP (VoIP) traffic with silence suppression. The proposed method uses power saving class (PSC) II during talk-spurt periods of parties A and/or B. On the other hand, during mutual silence periods, sleep interval placement is determined by the proposed probabilistic sleep interval decision (PSID) algorithm. Under the PSID algorithm, the length of sleep intervals in mutual silence period under the PSID algorithm is determined by the cumulative density function of the length of mutual silence period. We use Brady model that is an accurate model of the on-off characteristics of conversational speech, in order to obtain the CDF. The performances of HESM based on the PSID algorithm are evaluated by the energy consumption of an MS and the VoIP packet drop probability. Results show that the proposed HESMs reduce considerably the energy consumption of an MS compared to PSC II, while satisfying the QoS constraints on the VoIP packet drop probability for VoIP connection in the base station (BS). Specifically, the result shows that proposed HESM reduces the energy consumption of MSs by up to 25%.