Investigation of the underwater noise effecting the turkish strait system

INVESTIGATION OF THE UNDERWATER NOISE EFFECTING THE TURKISH STRAIT SYSTEM Serdar TOMBUL This study, which is prepared as a PhD thesis, mainly aims to identify and mapping the underwater noise effecting the Turkish Straits System including the Marmara Sea, İstanbul Strait and Çanakkale Strait for the first time. The Bosphorus and the Dardanelles Straits are noisier regions due to traffic density, port activities, and also current and turbulance of the flow. The types of ports, ship traffic and cabotage lines, anchorage areas, marinas and piers used for various purposes in the Sea of Marmara have been identified and mapped using navigation charts. According to the information obtained from these charts, a total of 122 underwater ambient noise records were taken from 51 different points. Noise recordings were taken for a minimum of 3 minutes at 5.89 Hz spectral resolution in the 1/3 octave band. Average values of sound pressure levels are calculated for 63 and 125Hz frequencies. The sound pressure levels reached the lowest level of the Marmara Sea at a distance of approximately 5 km. It was determined by using the sound propagation model. The sound pressure levels and distributions of different noise sources obtained from the measurements were matched with the noise sources map and a time-independent noise map for the Marmara Sea was obtained. According to these maps, it was determined that the southern part of the Sea of Marmara is the quietest (about 78 dB), while the straits and ship traffic line noise arithmetic mean reach up to 152 dB. With this project, for the first time, the underwater ambient noise map of the Marmara Sea was created with in-situ measurements.