Temporal variation of transmission loss by internal tide in the southern sea of Jeju island in summer

Abstract

Temporal variations of acoustic transmission loss (TL) affected by internal tide are simulated using oceanic data measured at two sites in the southern sea of Jeju island. Temperature and salinity were measured every hour for 25 hours during July 27th and 28th 2009. The periodic fluctuation of temperature due to the internal tide was observed and its vertical displacement was more than 10m. In order to investigate the variation of TL, acoustic propagation between two measurement sites (3.8 km distance) was computed at a source depth of 10 m. Acoustic propagation model RAM was used for the simulation. Standard deviations of TL variation were 4.2 dB and 3.7 dB for center frequencies of 100 Hz and 1 kHz with 1/3 octave band, respectively. The lower frequency was more correlated with the tidal period than the higher one. Detection range was also varied by the internal tidal, up to 1 km for the 60 dB detection level. These results imply that tidal variation of TL should be considered for acoustic researches at...