This paper explains the performance of voice over LTE system using different voice codec. LTE is the third generation partnership program 3GPP communication system which is wireless in nature and is also the first IP based system. VoLTE (Voice over LTE) is expected to be deployed in the near future for providing voice services. It's ability to reach high throughput is promising in both downlink and uplink so for ensuring that a good QoS is experienced by user, an efficient end-to-end model is required. There is also an increasing need for much higher data capacity as a result of smartphone industry growth. In this paper a 10×10 square kilometer campus is taken and by using OPNET modeler software different voice codec scenarios are simulated and their influences are seen on the LTE parameters like throughput, average jitter, end to end delay and MOS values which in turn helps to obtain an efficient voice service over the LTE system with little or no hitch.