Analyses of Internal Wave (IW) signatures by insitu observations off Visakhapatnam have been presented to study the impact of IWs on acoustic field. Temperature data were collected for 44 hours off Visakhapatnam (17° 26.46’N and 83° 31.20’E) and Bhimili (17°35.486’N, 83°42.322’E) at sonic depth 100 m during different seasons using time series CTD (hourly), current meter and indigenously developed thermister chain (at an interval of 2 minutes) to study the Internal Wave (IW) characteristics. Sound velocity realizations (in space and time) in the observed High Frequency (HF) IW field is generated utilizing Garret-Munk (GM) model. Acoustic propagation simulation is carried out in the IW HF field over 9 km (cycles) needed for navy objectives for different source-receiver configurations with cutoff frequency through field observations. Transmission loss anomaly with reference to mean are found to be 3-9 dB for normal conditions while 30 dB in disturbed conditions.