The jet noise is the main cause of the vibro-acoustic loading and internal noise (noise felt by the payload and critical launch vehicle systems) experienced by the launch vehicle during lift-off phase. Techniques such as water injection are being attempted to reduce the launch vehicle noise during lift-off and its impact on the sensitive payload and sub-systems of the launch vehicle are yet to be studied. The current work deals with estimation of noise levels on the entire launch vehicle using a modified version of Eldred’s method. The prediction algorithm takes into account the three dimensional nature of jet deflector and consequent distribution of noise sources. Effect of water injection on the noise levels is also attempted. Results show that due to the three dimensional nature of the sources, the noise levels on the front side are higher than on the umbilical tower side. Employment of water injection is found to decrease the noise levels upto 1.5dB at high frequencies
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