Sea surface motion induced effects on high frequency underwater acoustic signals

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Elektrik ve Elektronik Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2014

Öğrenci: HASAN GÜNEŞ

Danışman: TOLGA ÇİLOĞLU

Özet:

Acoustic signal scattering from the moving sea surface constitutes one of the most significant problems in underwater communication and sonar applications when dealing with signal processing especially at high frequencies. In this thesis, a realistic 3D linear sea surface wave model which solves governing equations is combined with a ray based computationally efficient acoustic model, BELLHOP, in order to simulate the effects of the time-evolving sea surface on acoustic waves. Rough sea surface realizations according to main environmental parameters (wind speed and fetch) are generated and imported into acoustic model to simulate temporal fluctuations in the acoustic signals. Doppler shifts in frequency of source signal are calculated by using the surface-normal velocities provided by sea surface wave model and acoustic rays provided by BELLHOP tool. Received timeseries are generated by convolution of source timeseries and time-varying impulse response of the underwater channel which is obtained from application of an existing interpolation scheme to arrival amplitude-delay pairs in order to simulate amplitude fluctuations as well. In addition, Monte Carlo based simulations are made to relate wind speed and acoustic signal fluctuations statistically.