Analysis and modeling of 255 source levels of merchant ships from an acoustic observatory along St. Lawrence Seaway

Abstract

An ensemble of 255 spectral source levels (SSLs) of merchant ships were measured with an opportunistic seaway acoustic observatory adhering to the American National Standards Institute/Acoustical Society of America S12.64-2009 standard as much as possible, and deployed in the 350-m deep lower St. Lawrence Seaway in eastern Canada. The estimated SSLs were sensitive to the transmission loss model. The best transmission loss model at the three measuring depths was an empirical in situ function for ranges larger than 300 m, fused with estimates from a wavenumber integration propagation model fed with inverted local geoacoustic properties for [300 to 1 m] ranges. Resulting SSLs still showed a high variability. Uni- and multi-variate analyses showed weak intermingled relations with ship type, length, breadth, draught, speed, age, and other variables. Cluster analyses distinguished six different SSL patterns, which did not correspond to distinctive physical characteristics of the ships. The broadband [20-500 Hz] source levels varied by 30 dB or more within all four 50-m length categories. Common SSL models based on frequency, length and speed failed to unbiasly replicate the observations. This article presents unbiased SSL models that explain 75%-88% of the variance using frequency, ship speed, and three other automatic identification system ship characteristics.

Estimates of Source Spectra of Ships from Long Term Recordings in the Baltic Sea

“…For Cargo and Tanker the variability of the measured source strengths is in the range of 20-30 dB above ∼200 Hz while increasing to >40 dB at around 100 Hz, agreeing with what is observed by Simard et al (2016). The observed Passenger ships notably show a smaller variability, not exceeding 20 dB for frequencies >200 Hz.…”

“…For the seabed, less high resolution data are available and estimates of the seabed structure and parameters were determined by a dedicated transmission loss measurement and geo-acoustic inversion. The approach is similar to that by Simard et al (2016), but employs a more elaborate procedure for estimating the seabed parameters motivated by the relative shallowness of the observation site (∼ 40 m). Furthermore, a wider range of ship types are included in the analysis, covering both passenger ferries and tugboats.…”

“…Examples of this are Hatch et al (2008), where measurements on ships off the coast of Massachusetts were combined with crude transmission loss (TL) estimates to establish the relative contribution of the URN from large vessels to the total ocean noise, and Wales and Heitmayer (2002) establishing an ensemble average spectrum based on recordings of 272 ships between 1986 and 1992 in the Mediterranean Sea and the Eastern Atlantic Ocean. Recently, Simard et al (2016) estimated source levels of 191 cargo ships and tankers passing the St. Lawrence Seaway during a 16 week period in 2012. More elaborate procedures for estimating URN as prescribed by the ANSI S12.64 (ANSI, 2009) standard have also been used.…”

Deep-water measurements of container ship radiated noise signatures and directionality

“…Surface-corrected broadband source levels (5-1000 Hz) may be derived from the surface-affected levels reported by McKenna et al (2012b) by adding 20 to 27 dB. This might explain why the surfaceaffected broadband source levels reported by McKenna et al (2012b) were found to be more than 15 dB lower than the source levels observed by Simard et al (2016). In addition, the inclination-angle dependence of the surface-affected source levels might further explain why at an inclination angle of about 0.2 (8 m depth) (Veirs et al, 2016) observed lower source levels (up to 15 dB) than McKenna et al (2012b) at 10 and Arveson and Vendittis (2000) at 90…”

Underwater Noise Modeling in Lithuanian Area of the Baltic Sea

“…Šiuo metu yra žinoma nemažai sudėtingų fizikinių povandeninio triukšmo modelių (Jensen et al 2011;Carey, Evans 2011;Etter 2012), tačiau supaprastintų priemonių, skirtų povandeniniam triukšmui modeliuoti bei aplinkos būklei vertinti, vis dar yra nedaug (Erbe et al 2012). Šiuo tikslu Klaipėdos universitete buvo pradėtas kurti supaprastintas povandeninio triukšmo modelis, kurį taikant galima prognozuoti laivų sukeliamo triukšmo lygius erdvėje, pasitelkiant jau turimą kitų šalių patirtį (Erbe et al 2014;Gervaise et al 2015;Simard et al 2016). Šio modelio programavimas buvo suskirstytas į 3 etapus: 1) programinio modulio, skirto automatinės identifikavimo sistemos (AIS) laivų registravimo duomenims apdoroti bei laivų triukšmo lygiams (GSL) tiriamoje vietovėje apskaičiuoti, sukūrimas; 2) modulio, skirto triukšmo lygių vidurkiams apskaičiuoti priklausomą triukšmo sklidimą, įtraukiant mažo gylio atkirtimo dažnio bei žemo dažnio korekcijas; 3) apskaičiavo triukšmo lygių vidurkius bei statistinius duomenis langeliuose bei erdvinį duomenų tinklelį toliau apdoroti (kartografuoti).…”