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1
Content available The imaging of Gdansk Bay seabed by using side sonar
Grelowska G., Kozaczka E., Witos-Okrasińska D., Szymczak W.
Polish Maritime Research
|
2018
|
S 1
111--118
EN
This paper is mainly aimed at presentation of an impact of environmental conditions on imaging accuracy by using hydro-acoustic systems in waters of a high non-uniformity of spatial distribution of hydrological parameters. Impact of refraction on erroneous estimation of range, in case of wave radiation into water under a large angle, like in side sonars or multi-beam echo-sounders, is especially important. In this paper seasonal changes in sound speed and its impact on acoustic beam refraction is discussed. And, examples which illustrate errors in determination of side sonar range occurred during last investigations carried out in Gdansk Bay waters are presented.
2
Content available Propagation of ship-generated noise in shallow sea
Kozaczka E., Grelowska G.
Polish Maritime Research
|
2018
|
nr 2
37--46
EN
Contamination of sea environment by noise and any energy radiated to water constitutes today a problem to which more and more attention is paid, in view, a.o., of consequences of an impact of these factors onto marine fauna. European Union has introduced a directive by which EU countries are made responsible to undertake efforts aimed at reaching a good envirenmental status of European seas by 2020. A main source of underwater noise is sea transport of any kind. Propagation of underwater acoustic disturbances in the Baltic Sea highly differs from the course of the phenomenon in a deep sea. Model of spherical propagation cannot be applied to this case in view of water environment limitation by seabed and free water surface, i.e. a reduction of the problem to wave propagation in a water layer of the depth comparable with acoustic wave length. This paper is aimed at demonstration of possible assessment of range of acoustic disturbances generated by a ship sailing in shallow sea, by using a method described in the work [13]. The research was made on the basis of results of own measurements of underwater noise produced by ships in the Gdansk Bay area. An important factor which decIdes on a range of underwater disturbances is a kind of seabed sediments. In this paper there are presented results of numerical investigations based on real data dealing with noise produced by a selected floating unit (ship) for selected characteristic spectral components. The simulations were conducted for the shallow sea model of definite physical parameters such as acoustic wave propagation velocity, geometrical dimensions (water depth) and seabed acoustic parameters as well.
3
Content available Influence of natural conditions on the imaging of the bottom of the Gdańsk Bay by means of the side scan sonar
Witos-Okrasińska D., Grelowska G., Kozaczka E.
Polish Maritime Research
|
2018
|
S 1
104--110
EN
The interest in underwater resources is the reason for the development of modern hydroacoustic systems, including side sonars, which find numerous applications such as: research of seabed morphology and sediment characteristics, preparation of sea sediment maps, and even in special cases of biocenoses such as sea grass meadows, detection of specific targets at the bottom such as shipwrecks, mines, identification of suitable sites for maritime infrastructure. Such applications require precise information about the position of the objects to be observed. Errors affecting the depiction of the bottom using hydroacoustic systems can be divided into errors associated with improper operation of measuring and support devices, systematic errors and random errors. Systematic errors result from the changing conditions prevailing in the analyzed environment affecting the measurement system. The errors affecting the correct operation of hydroacoustic systems can include: changing angle of inclination of the beam caused by the vessel’s movement on the wave or refraction connected to changes in the sound speed as the depth function.
4
Content available Theoretical model of acoustic wave propagation in shallow water
Kozaczka E., Grelowska G.
Polish Maritime Research
|
2017
|
nr 2
48--55
EN
The work is devoted to the propagation of low frequency waves in a shallow sea. As a source of acoustic waves, underwater disturbances generated by ships were adopted. A specific feature of the propagation of acoustic waves in shallow water is the proximity of boundaries of the limiting media characterised by different impedance properties, which affects the acoustic field coming from a source situated in the water layer “deformed” by different phenomena. The acoustic field distribution in the real shallow sea is affected not only by multiple reflections, but also by stochastic changes in the free surface shape, and statistical changes in the seabed shape and impedance. The paper discusses fundamental problems of modal sound propagation in the water layer over different types of bottom sediments. The basic task in this case was to determine the acoustic pressure level as a function of distance and depth. The results of the conducted investigation can be useful in indirect determination of the type of bottom.
5
Content available Acoustic imaging of selected areas of Gdansk Bay with the aid of parametric echosounder and side-scan sonar
Grelowska G., Kozaczka E., Szymczak W.
Polish Maritime Research
|
2017
|
nr 4
35--41
EN
The article presents and analyses the data recorded during sounding of the Gdansk Bay seabed with the aid of a parametric echosounder and a side-scan sonar. The accuracy of seabed structure examination, as a condition for obtaining valuable results, requires correct configuration of echolocation devices and proper calibration of peripheral devices, such as the survey unit geographical position sensor – GPS, the navigation unit, the MRU-Z sensor of pitch, roll and heave, and the sound velocity meter, which deliver the data to the bathymetric measurement system. Parametric seabed profilers deliver two types of data: the envelope, and the detailed echo signal without processing. The envelope is used for data visualisation in the form of online echograms, while the echo signal is stored for further analyses, to be performed using dedicated software or, after relevant conversion, in arbitrary programming environment1. The presented data analysis is illustrated by selected sample images recorded by the parametric echosounder and the side-scan sonar during Gdansk Bay sounding.
6
Content available Study of seasonal acoustic properties of sea water in selected waters of the southern Baltic
Grelowska G.
Polish Maritime Research
|
2016
|
nr 1
25--30
EN
Climate Research of the globe is a current task, in particular to confirm the general hypothesis of global warming associated with an increase in average temperature. The sea acoustic climate is derived from the concept of climate and refers to the conditions of propagation of acoustic waves in a particular basin. In this paper, the results of systematic measurements of temperature, salinity and velocity distributions of sound in the area of the southern Baltic will be present. The focus will be on the results of extensive measurements carried out „in situ” in particular.
7
Content available Investigation of the vertical distribution of the sound speed of the Gulf of Gdansk in the years 2000-2010
Grelowska G., Witos D.
Hydroacoustics
|
2016
|
Vol. 19
129--137
EN
The conditions of the acoustic wave propagation in the southern Baltic are much more complex than in other shallow waters. In the typical shallow water, seasonal changes in acoustical conditions in the upper layer, of the depth of about 60-70 m, are observed. They are caused by variation of the annual meteorological conditions. Most often, in the deep water layer, acoustical conditions are stable throughout the year. However, in the Southern Baltic they change during the year also in the deep water layer. They depend on the inflows of highly saline water from the Northern Sea through the Danish Straits, which evoke a dense bottom current increasing the salinity at the bottom. The vertical sound speed distribution in the Southern Baltic is strongly dependent on the hydrological conditions. In the paper the characteristic elements of acoustic climate of the Southern Baltic will be considered, based on data concerning the Gulf of Gdansk. Averaged characteristics of temperature, salinity and sound speed for the years 2000-2010, as well as anomalies, have been determined.
8
Content available In Memoriam Professor Ignacy Gloza
Kozaczka E., Grelowska G.
Archives of Acoustics
|
2016
|
Vol. 41, No. 4
813--815
EN
On 4th November 2016 Professor Ignacy Gloza passed away. He was a wonderful person, still full of creative powers, committed to researchwork in hydroacoustics carried out in cooperation with Polish and foreign research institutes.
9
Historyczny przegląd rozwoju systemów akustyki podwodnej
Grelowska G., Kozaczka S.
Logistyka
|
2015
|
nr 4
1649--1652, CD2
PL
W artykule przedstawiono informacje o początkach hydroakustyki, gałęzi nauki i techniki niezastąpionej jako narzędzie eksploracji i eksploatacji mórz i oceanów. Zaprezentowano najważniejsze odkrycia naukowe, dzięki którym powstać mogły urządzenia i systemy hydroakustyczne, a także pierwsze doświadczenia i pierwsze systemy obserwacji podwodnej.
EN
The article presents information about the origins of hydroacoustics, branches of science and technology as a irreplaceable tool for exploration and exploitation of the seas and oceans. Paper presents major scientific discoveries in the field of hydroacoustic devices and systems, as well as first experiences and the first underwater observation systems.
10
Content available Tracking of the broadband source of the underwater noise in the very shallow water conditions
Grelowska G., Kozaczka E.
Hydroacoustics
|
2015
|
Vol. 18
77--86
EN
The paper contains the results, both theoretical and experimental, connected with the tracking of the underwater noise source as small ships, pontoon, diver and so on. The problem of security in the shallow water area is the challenge for underwater acousticians. In this paper there is taken into account the detection of the sources that move on the surface of the sea or underwater in shallow and very shallow water. The main goal deals with characterization of the sound propagation at the shallow water channel. The next problem is formulation of the sound propagation inside of this acoustic duct including normal mode creations and dispersion of the acoustic energy. When we take into account the small ships noise the two main sources are analyzed. The first one is the vibration energy produced by the mechanisms located inside of the ship hull. The acoustical energy is transformed through structural elements of the hull to surrounding water. This energy propagates as broadband underwater noise. The next source is the ship propeller. The sources of the underwater noise give the some deposit to the total acoustical energy that means the ambient noise. The problem that should be solved is to discover these acoustical disturbances along with their classification, identification and tracking.
11
Content available Study of Noise Propagation for Small Vessels
Weryk M., Kozaczka E., Grelowska G.
Archives of Acoustics
|
2015
|
Vol. 40, No. 2
267--272
EN
The paper presents the results of the noise propagation analysis in ship structures tested in a number of AHTS (Anchor Handling Tug Supply) vessels. Statistical Energy Analysis (SEA) based on numerical model developed specially for the purpose of this numerical investigation were conducted. This numerical model enabled the analysis of both the structural elements and the acoustic spaces. For the detailed studies 47 points fixed at various ship locations were selected. Prediction results with use of the numerical model were compared with the experimental results carried out in six identical AHTS vessels. Experimental studies were performed in accordance with the requirements of the International Maritime Organization (IMO) Resolution A.468 (XII). As a result one presented a comparison of the model analysis and experimental tests results.
12
Content available Nonlinear Properties of the Gotland Deep : Baltic Sea
Grelowska G., Kozaczka E.
Archives of Acoustics
|
2015
|
Vol. 40, No. 4
595--600
EN
The properties of the nonlinear phenomenon in water, including sea water, have been well known for many decades. The feature of the non homogeneous distribution of the speed of sound along the depth of the sea is very interesting from the physical and technical point of view. It is important especially in the observation of underwater area by means of acoustical method (Grelowska et al., 2013; 2014). The observation of the underwater space has been carried out for more than hundred years. In the second half of the twentieth century we observed very intense trend of development of the measuring methods of underwater sound speed. It was done mainly in the linear sound propagation aspect. At the end of 20th century nonlinear devices were invented. Thus, from this point of view, knowledge on the nonlinear properties of the sea water is the matter of interest. The phenomenon of nonlinear distortion of elastic waves, and the same the efficiency of nonlinear transfer of energy from the primary wave to the higher harmonic components depend on properties of the medium, especially on the material constant known as the nonlinearity parameter B/A. The Baltic Sea is a specific reservoir with untypically low salinity and low depth (Grelowska, 2000). In the paper results of investigation of nonlinear properties of the South and the Central Baltic by means of thermodynamic method are presented.
13
Content available Radiation of high intensity sound by circular disc by means of the numerical method
Grelowska G., Kozaczka E.
Hydroacoustics
|
2014
|
Vol. 17
79--92
EN
The main goal of this paper is to find sound pressure distribution radiated by the circular piezoelectric disc that vibrates with the finite amplitude. There has been presented the pressure distribution close to the radiating surface. Also it is shown the sound pressure distribution in the 3D form. The mathematic modeling was carried out on the base of the nonlinear acoustic equation with the proper boundary condition. The axial symmetry of radiation was assumed. The results have been shown in the form of pressure distribution at different distances from the source. The final results will be applied to the designing of the underwater sources of finite amplitude.
14
Content available Investigation of bottom sediment stratification
Grelowska G., Kozaczka E.
Hydroacoustics
|
2014
|
Vol. 17
93--103
EN
The main goal of this paper is to find a method to assess remotely the type of sediments on the basis of the signal received using the parametric echosounder. The images of the sea bottom sediments taken by a parametric echosounder show the fine structure of the upper layer of the bottom sediments. The depth of penetration depends on the type of sediment, in fact on the attenuation of acoustic wave. In the paper the method of distinguishing the sediment layer basing on interpretation the received bottom signal is proposed. The knowledge on acoustic parameters of different type of sediments obtained in laboratory condition or using the literature data, allows to predict the composition of upper layer of the bottom. The considerations are illustrated by the results recorded from the bottom of the Gulf of Gdansk.
15
Content available Underwater Acoustic Imaging of the Sea
Grelowska G., Kozaczka E.
Archives of Acoustics
|
2014
|
Vol. 39, No. 4
439--452
EN
Acoustic waves are a carrier of information mainly in environments where the use of other types of waves, for example electromagnetic waves, is limited. The term acoustical imaging is widely used in the ultrasonic engineering to imaging areas in which the acoustic waves propagate. In particular, ultrasound is widely used in the visualization of human organs – ultrasonography (Nowicki, 2010). Expanding the concept, acoustical imaging can also be used to presentation (monitoring) the current state of sound intensity distribution leading to characterization of sources in observed underwater region. This can be represented in the form of an acoustic characteristic of the area, for example as a spectrogram. Knowledge of the underwater world which is built by analogy to the perception of the space on the Earth’s surface is to be systematize in the form of images. Those images arise as a result of graphical representation of processed acoustic signals. In this paper, it is explained why acoustic waves are used in underwater imaging. Furthermore, the passive and active systems for underwater observation are presented. The paper is illustrated by acoustic images, most of them originated from our own investigation.
16
Content available Gdansk Bay sea bed sounding and classification of its results
Grelowska G., Kozaczka E., Kozaczka S., Szymczak W.
Polish Maritime Research
|
2013
|
nr 3
45--50
EN
The main goal of this paper is to describe the results of sounding the Gdansk Bay sea bed by using a SES- 2000 Standard parametric sub-bottom profiler. Quality of data obtained during trials depends inter alia on a proper location of transducer array to reduce influence of pitch, roll and heave motions as well as ship self noise (resulting from bubbles due to propeller and flow around hull, vibration generated by main engine and auxiliary devices). Furthermore, calibration of complementary units such as GPS, heading sensor, MRU-Z motion sensor and navigation devices make sea-bed investigating system capable of working with its whole capability. Results of so prepared surveys have been presented and discussed. They contain also an elaborated map of Gdansk Bay with preliminarily classified sea-bed materials and description of most interesting areas.
17
Content available Underwater Noise Generated by a Small Ship in the Shallow Sea
Grelowska G., Kozaczka E., Kozaczka S., Szymczak W.
Archives of Acoustics
|
2013
|
Vol. 38, No. 3
351--356
EN
Study of the sea noise has been a subject of interest for many years. The first works in this scope were published at the turn of the twentieth century by Knudsen (Knudsen et al., 1948) and G. Wenz (Wenz, 1962). Disturbances called “shipping noise” are one of the important components of the sea noise. In this work the results of an experimental research of underwater noise produced by a small ship of a classic propulsion are presented. A linear receiving antenna composed of two orthogonal components was used in the investigation. Identification of the main sources of acoustic waves related with the ship was achieved. In addition, the intensity of the wave was measured. The research was performed in conditions of the shallow sea.
18
Content available Detection of Objects Buried in the Sea Bottom with the Use of Parametric Echosounder
Kozaczka E., Grelowska G., Kozaczka S., Szymczak W.
Archives of Acoustics
|
2013
|
Vol. 38, No. 1
99--104
EN
The paper contains results of a in situ research main task of which was to detect objects buried, partially or completely, in the sea bottom. Object detecting technologies employing acoustic wave sources based on nonlinear interaction of elastic waves require application of parametric sound sources. Detection of objects buried in the sea bottom with the use of classic hydroacoustic devices such as the sidescan sonar or multibeam echosounder proves ineffective. Wave frequencies used in such devices are generally larger than tens of kHz. This results in the fact that almost the whole acoustic energy is reflected from the bottom. On the other hand, parametric echosounders radiate waves with low frequency and narrow beam patterns which ensure high spatial resolution and allows to penetrate the sea bottom to depths of the order of tens of meters. This allows to detect objects that can be interesting, among other things, from archaeological or military point of view.
19
Content available Processing data on sea bottom structure obtained by means of the parametric sounding
Kozaczka E., Grelowska G., Kozaczka S., Szymczak W.
Polish Maritime Research
|
2012
|
nr 4
3-10
EN
The aim of the paper is to analyze data obtained during sounding the Gdansk Bay sea bed by means of the parametric echo-sounder. The accuracy of the sea bottom structure investigation needs correct configuration of research equipment and proper calibration of peripheral devices (GPS, heading sensor, MRU-Z motion sensor and navigation instruments which provide necessary data to bathymetrical measurement system, enabling its work with full capability. The parametric sub-bottom profiler delivers two types of data which include different information: envelope and pure echo signal sampled without processing. The first is used to present echograms in real time and the second one is stored during sounding and the obtained data can be analyzed by using post-processing software. Differences in the results are presented and discussed. And, are described also criteria taken into account during determination of the measurement areas and selection of different configurations of the software according to the information to be obtained from trials. Complementary information can be achieved from processing the data by means of the procedures offered by Matlab software, which allows for a clear 3D presentation of the results. The consideration are illustrated by echograms taken in the natural conditions.
20
Content available Methods of data extraction from sub-bottom profiler’s signal
Grelowska G., Kozaczka E., Szymczak W.
Hydroacoustics
|
2010
|
Vol. 13
109-118
EN
Data obtain during sounding Gdańsk Bay with SES-2000 Standard parametric sub-bottom profiler has two types of information: envelope and pure signal. First is used to plot echograms in real time and contain envelope of echo. The second one is stored during sounding and can be processed after recording data. Comparison of results will be shown and discussed. First step in investigation was proper configuration of small measurement vessel detailing localization of echosounder antennas and perypherical units (GPS, heading, motion sensor MRU-Z and navigation devices) complementing information of measurement system. There are different types of research (for example looking for buried objects or investigation of sediments layers) which require separate configuration of software working with sub-bottom profiler. Various settings will be presented and interrelated with real data. Very important in work with stored sounding data is proper post-processing realized with software dedicated to parametric echosounder SES-2000 standard and Matlab which give possibility of clear presentation in 3D with precise measurement methods what will be presented on echograms coming from works on sea in 2009 year.
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