Gemi Akustik İz Analizi

Year 2017, Volume: 7 Issue: 13, 25 - 31, 30.06.2017

Umut Fırat Tayfun Akgül

Abstract

Pervane ve makine kaynaklı gemi gürültülerinden çıkarılan frekans hatları su altı hedef sınıflandırmada kullanılan en önemli verilerdir. Kavitasyon sonucu ortaya çıkan genlik modülasyonlu geniş bant pervane gürültüsü zımnen pervane tonellerini içerirken gemi itki sistemi ve yardımcı makinelerinin su altına yayılan dar bant bileşenleri  makine tonellerini  oluşturur. Zarf tespitine dayalı Demon ve alçak frekans analizine dayalı Lofar yöntemleri sırasıyla pervane ve makine tonellerinin tespiti için başvurulan temel yöntemlerdir. Bu çalışmada, bu iki yöntemin hedef sınıfını belirlemede nasıl kullanılabileceği İstanbul Boğazı'nda kaydedilmiş gerçek gemi gürültülerinden yararlanılarak tartışılmaktadır. Farklı tipte gemilerin farklı frekanslarda pervane ve makine tonelleri ürettiği gösterilmiştir. Yaşanan başlıca zorluklar arasında, durağan olmayan sinyallere yol açan çevresel şartlar ve gemi gürültülerinin kontrollü deneylerle kaydedilmemiş olması sayılabilir. Gelecek çalışmalarda bu zorlukları aşmak için farklı yöntemler denenmelidir.

Keywords

Gemi gürültüsü, Demon, Lofar

Ship Acoustic Signature Analysis

Abstract

The frequency lines extracted from ship-radiated propeller and machinery noise give the essential information for underwater target classification. Amplitude modulated broadband propeller noise imposed by cavitation contains the implicit propeller tonals while underwater-radiated narrowband propulsion and auxiliary machinery noise gives rise to machinery tonals. Detection of these propeller and machinery tonals are mainly handled by an envelope detection method, Demon and by a low frequency analysis method, Lofar, respectively. In this paper we discuss the utilization of these methods on the identification of targets employing real-world ship noise recorded in the Strait of Istanbul. We showed that different ship types yield different propeller and machinery tonal frequencies. Main challanges are environmental conditions causing nonstationary signals as well as lack of data from controlled experiments. Thus, future work should include the investigation of suitable methods to cope these challenges.

Keywords

Ship-radiated noise, Demon, Lofar

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