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Wyszukujesz frazę "marine acoustics" wg kryterium: Wszystkie pola


Wyświetlanie 1-6 z 6
Tytuł:
The „Bionic Sonar” project, phase one: Initial research on Marine Mammal Acoustics
Autorzy:
Nowak, Ł.
Pawłowski, P.
Penkowski, M.
Kosecka, M
Skóra, K. E.
Powiązania:
https://bibliotekanauki.pl/articles/331704.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Results of theoretical and experimental investigation on marine mammal acoustics are presented and briefly concluded. The described research is a part of interdisciplinary scientific project titled „Bionic Sonar”. The goal of the project is to develop a new kind of hydroacoustic sources with specified frequency characteristics and directivity patterns, inspired by the vocal and echolocation systems of the marine mammals. The presented theoretical investigation focuses on underwater communication and navigation capabilities of dolphins and grey seals. The experimental research concerning underwater vocalizations of the grey seals was performed in the Hel Marine Station of the Institute of Oceanography of the University of Gdańsk. Underwater sounds were recorded using hydrophones placed in the pools in which only the grey seals were present. The recorded vocalizations have been extracted from the recordings and analyzed for a number of distinguishing characteristics. The obtained results are compared to the results of other related investigations described in literature.
Źródło:
Hydroacoustics; 2013, 16; 189-196
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An Autonomous Hydroacoustic System for studying long-term scattering variability
Autorzy:
Szczucka, J.
Groza, K.
Porazinski, K.
Powiązania:
https://bibliotekanauki.pl/articles/48119.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Oceanologii PAN
Tematy:
marine acoustics
bottom
Autonomous Hydroacoustic System
vertical migration
scattering
sea surface
Baltic Sea
water column
Opis:
A new instrument, an Autonomous Hydroacoustic System, was designed to probe a water column acoustically from the bottom to the sea surface. It is capable of operating from a depth of 100 m self sufficiently for up to 10 days. A brief description of its construction and electronic design is provided. Preliminary results from the first field study consisting of a 90-hour series of backscattering measurements are presented.
Źródło:
Oceanologia; 2002, 44, 1
0078-3234
Pojawia się w:
Oceanologia
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On a threshold induced bias in fish target strength estimation
Autorzy:
Moszyński, M.
Powiązania:
https://bibliotekanauki.pl/articles/332238.pdf
Data publikacji:
2003
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
fisheries acoustics
marine organisms
Opis:
In fisheries acoustics the bias introduced by a system threshold in the integration of echoes from fish and other marine organisms has long been recognized. Some simple methods for evaluating such a bias uses Rayleigh assumption applied to fish backscattering length distribution. More adequate methods require that the target strength distribution of the fish and directivity pattern of the transducer be known. The method proposed here uses statistical approach for correction of target strength probability density function (PDF). The theory of conditional target strength PDF and conditional beam pattern PDF is derived. It provides correction not only for mean value of target strength but for whole distribution. The data obtained from simulations are presented and compared with those obtained from single-beam inverse processing.
Źródło:
Hydroacoustics; 2003, 6; 49-52
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Marine Mammals Classification using Acoustic Binary Patterns
Autorzy:
Nadir, Maheen
Adnan, Syed M.
Aziz, Sumair
Khan, Muhammad Umar
Powiązania:
https://bibliotekanauki.pl/articles/1953520.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
marine mammals
1D Local Binary Patterns
Mel frequency cepstral coefficients
feature extraction
passive acoustic monitoring
Opis:
Marine mammal identification and classification for passive acoustic monitoring remain a challenging task. Mainly the interspecific and intraspecific variations in calls within species and among different individuals of single species make it more challenging. Varieties of species along with geographical diversity induce more complications towards an accurate analysis of marine mammal classification using acoustic signatures. Prior methods for classification focused on spectral features which result in increasing bias for contour base classifiers in automatic detection algorithms. In this study, acoustic marine mammal classification is performed through the fusion of 1D Local Binary Pattern (1D-LBP) and Mel Frequency Cepstral Coefficient (MFCC) based features. Multi-class Support Vector Machines (SVM) classifier is employed to identify different classes of mammal sounds. Classification of six species named Tursiops truncatus, Delphinus delphis, Peponocephala electra, Grampus griseus, Stenella longirostris, and Stenella attenuate are targeted in this research. The proposed model achieved 90.4% accuracy on 70-30% training testing and 89.6% on 5-fold cross-validation experiments.
Źródło:
Archives of Acoustics; 2020, 45, 4; 721-731
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental Study of Identifying Emission Sources of Acoustic Signals on the Cylinder Body of a Two-Stroke Marine Diesel Engine
Autorzy:
Dong, Xuan Thin
Nguyen, Manh Hung
Powiązania:
https://bibliotekanauki.pl/articles/1953513.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
acoustic emission
two-stroke marine diesel engine
experimental method
low-to-high frequency ranges
medium-to-high frequency ranges
vibration
Opis:
In this paper, an experimental method was utilized to investigate acoustic emission (AE) characteristics and to identify emission sources of the nonlinear AE signal on the cylinder body of a large low-speed two-stroke marine diesel engine in real-working conditions on the sea in misfiring and normal firing modes. Measurements focused on the AE signal acquired in a transverse direction in low-frequency (20-80 kHz), medium-frequency (100-400 kHz) and high-frequency (400-900 kHz) ranges. The collected signals were analyzed on the crank angle and crank angle-frequency domains. The results showed that all potential sources of the nonlinear AE signal could be mapped in the low-frequency range. However, only the AE signal caused by the combustion process at around the top dead center could be well-observed in the medium-to-high-frequency range. The findings also revealed that in normal firing conditions, the AE energy radiated by friction in the down-stroke period was smaller than in the up-stroke process due to gas-sealing forces. Moreover, the AE energy in the misfiring condition was higher than in the normal firing state. These outcomes considerably contributed understandings to characteristics of friction and wear around the mid-stroke area of the cylinder on a two-stroke marine diesel engine.
Źródło:
Archives of Acoustics; 2021, 46, 1; 105-119
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Design and Numerical Simulation of the Performance of Acoustic Plenum Chamber of a Marine Gas Turbine Air Supply System
Autorzy:
Rasoulimoghadam, Mehrdad
Kheradmand, Saeid
Powiązania:
https://bibliotekanauki.pl/articles/176931.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
aeroacoustics
large eddy simulation
Lighthill analysis
Ffowcs Williams model
Hawkings model
propagation of wave in duct
Opis:
In the present work, an approach to obtain a design method for the size of the plenum chamber cross-section of a marine gas turbine air supply system has been investigated. Flow in ducts makes noise which is very high in the turbine inlet part because of the large amount of flow. Therefore, this phenomenon should be considered in the design process. A suitable approach to design the duct is proposed (considering acoustic and aerodynamic performance at the same time). In this method, an air supply channel system of the marine gas turbine has been categorized into three sections according to the requirements of the aerodynamic and acoustic; inlet, plenum chamber, and outlet channels with circular cross-sections. The geometrical dimensions of inlet and outlet channels have been determined using the plane waves theory about a channel, in which the effects of flow is ignored. Space limitations of battleships at the dominant frequency have been considered. Then, the optimized size of the mid-channel section, in terms of both aerodynamic and acoustic requirements, using numerical methods and regarding the effects of flow has been calculated. Various 3D turbulent flows inside the plenum chamber have been considered, in which large eddy simulation turbulence model is utilized. Ffowcs, Williams and Hawkings models are used for the sound propagation process based on the Lighthill integral equation. The validity of the simulation has been checked by comparing results (sound pressure level) with experimental data obtained from a chamber. The comparison revealed the acceptable errors for a variety of frequencies. The results disclosed that the performance of channel system aerodynamic decreased when the fraction of plenum chamber cross-section to inlet/outlet channel cross-section increased. With an increase in the cross-section size at first Acoustic performance is improved and then worsen. Six different cases of marine gas turbine air supply system configurations have been presented, in which the limitation of the battleship space is considered. Examining and comparing the acoustic performance of different cases of the air supply channel system, it was found that the amount of sound pressure level, around the air supply channel system, and the high-pressure sound area can move along the air supply channel system. Additionally, deviations from plane waves considering the effects of flow have been inspected in all cases. The reason for this deviation is the effects of the airflow through the channel system and quadrupole sources in the production of sound in the channel system, which causes higher modes.
Źródło:
Archives of Acoustics; 2019, 44, 4; 793-806
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-6 z 6

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