2014 / 6

Central museum of musical culture in Moscow has 2 concert premises: the Organ hall, where the the pipe organ was installed in 1979 by the German organ-building company «Alexander Schuke», and the Concert foyer of the 1st floor, where concerts are held from 1998, when the historic organ built by Friedrich Ladegast in 1868 was installed after the restoration. The results of acoustical measurements made in the Organ hall before rebuilding of 2004 and after rebuilding, and in the Concert foyer are represented. It is shown that the acoustical characteristics of the Organ hall became worse after rebuilding of the hall. The recommendations to improve the acoustics of the Organ hall are proposed. The acoustical characteristics of the Concert foyer are good enough for the historic Ladegast organ.  Hide Abstract 

A number of endeavor studies on increase of the sound transmission loss of the fuselage panel is carried out. Optimum variants of the vibrodamping materials fastenings on a fuselage construction from the point of view of noise reduction into the aircraft are defined. The results showing essential increase of the sound transmission loss of the fuselage panel at a certain way of fastening of the interior panel in the wide range of frequencies are received. Techniques of carrying out such researches in reverberation rooms are fulfilled. Hide Abstract 

Currently in Russia to accelerate and simplify the calculations of acoustic ambient noise using a variety of software products both domestic and foreign design. Often, when using these software products is not possible to verify the correctness of the implementation of algorithms and calculations of the results obtained. In this regard, the International Organization for Standardization in 2012 put the topic on the development of standards to specify the requirements for data quality software products and regulatory criteria for their testing. Similar topic is included in the plan of national standardization on 2013 - 2014 gg In the framework of a draft standard that would allow to evaluate the method implemented in software used on the territory of the Russian Federation, calculation methods, and to do the calculations themselves as open and transparent. This report describes the results of the work performed, the basic provisions of the draft standard. We also consider the question of a unified data format, which would allow you to transfer and synchronize the results and raw data between different software tools. Hide Abstract 

The work is devoted to the study of absorption characteristics of the Helmholtz resonator in the channel. Discusses models of the Helmholtz resonator with and without taking into account the presence in the cavity resonator the wall boundary layer. The results of the calculations are compared with experimental data obtained when measuring the acoustic properties of the resonator in the impedance tube. Hide Abstract 

Patterns related to the nature of vortex sound (Aeolian tone) generated by airflow interaction with cylinder providing vortices separation from profile surface and their transformation to vortex street in the wake are considered. Locations of vortex street formation place in the wake and dimensions of street instability regions are estimated. It is shown that inside Reynolds number range under analysis (4.7 103 – 1.5 104) pressure fluctuations maximum in the wake approaches cylinder surface with flow velocity increase augmenting fluctuation pressure level on cylinder surface together with vortex sound level observed outside. It is demonstrated that impact on wake vortex street by introduction of obstacle in its initial instability region leads to visible vortex sound intensity decrease right up to process total cancellation.  Hide Abstract 

Spatiotemporal dynamics of three wind velocity components, longitudinal and transverse structure functions of the wind velocity field, structure characteristics of temperature and wind velocity, turbulent kinetic energy dissipation rate, and outer scales of temperature and dynamic turbulence is analyzed in the atmospheric boundary layer. A closed iterative algorithm of sodar data processing is used that takes into account the turbulent attenuation of acoustic waves propagating along the sounding path and allows vertical profiles of the structure characteristics of temperature and wind velocity fields to be reconstructed simultaneously and hence their interrelation to be investigated. The efficiency of the suggested algorithm is confirmed by a comparison of the results obtained with the data of lidar sensing and by the agreement of the results obtained with the available theoretical estimates. Hide Abstract 

A hardware-software complex intended for monitoring of meteorological conditions in a limited territory is described. A number of information-measuring systems providing a solution of the given problem are considered: meteorological devices for measuring the parameters of the surface and boundary layers of the atmosphere, mathematical methods, and models. A review of the existing systems and systems being developed is presented. Various meteorological systems of in situ and remote types intended for monitoring of the state of the surface and boundary layers of the atmosphere, approaches to the design of measuring system networks, and methods of forecasting of the meteorological conditions in the limited territory are also considered and analyzed.  Hide Abstract 

Discusses the sources of error when ultrasonic measurements of meteorological measurements in the atmosphere: method related to the physics of ultrasound propagation in the atmosphere; radio signals that occur when recording and processing electrical signals equipment, mechanical, due to the influence of the construction of the device on the wind flow and wrapping thanks to its temperature changes and others. Mathematical algorithms and methods are described that allow you to minimize measurement errors. The presentations are illustrated with materials from industrial development experience weather station AMK-03. Hide Abstract 

The paper presents information about the Chelyabinsk meteoroid impact on February 15, 2013. Described here are similar infrasound effects, recorded earlier, and the methods of their interpretation. The paper also gives characteristics of the ISTP SB RAS infrasound installation which recorded the effect of the meteor’s explosion in the atmosphere. Besides, we present the coherent infrasound signal and discuss its parameters. Hide Abstract 

Previously, algorithms of emission seismic tomography have been developed and tested successfully in geophysical investigations. It was found that intense sources of man-made seismic radiation creates shielding effect and prevents monitoring of weak endogenous sources associated with the process of fluid transport and reaction of the medium to changes in the stress-strain state. The results of numerical simulation and analysis of field data show that special methods of spatial filtering allows us to take the shielding effect of and visualize weak endogenous sources. Spatial filtering methods because of its features are sensitive to the density of the observing system and its geometry. Under adverse conditions algorithms can lose efficiency. Numerical simulation shows how you can upgrade the small seismic array set on an area of the geodynamic observatory to rectify the situation. It turned out that a slight increase in the number of points of observation and correct their arrangement can completely recover performance of the filter algorithms and ensure the correct operation of the system under intensive man-made interference.  Hide Abstract 

Results of investigation of geoacoustic emission, which has been carried out since 1999 in Kamchatka, are presented. The particularity of experiments is application of broadband piezo-ceramic hydrophones installed near the bottom of natural and artificial reservoirs for registration of emission. Application of the receivers of such type allowed us to expand frequency range of registration from 0.1 Hz to 11 kHz. During the investigations the relation between activation of deformation processes in the near surface sedimentary rocks and high-frequency anomalies in geoacoustic signals was identified. It is observed the most vividly during final stage of earthquake preparation. Hide Abstract 

Problem of seismoacoustic wave’s excitation in a layered system composed of homogeneous isotropic elastic half-space – homogeneous fluid layer – fluid half-space, by harmonic force acting on elastic medium is considered. This system simulates Earth, near-surface layer of air with sharp temperature contrast and atmosphere. Expressions for wavefields obtained in the form of Fourier – Bessel integrals. Focus is concentrated on study of acoustic waves in the fluid half-space. Approximate solution valid on large (in comparison with the wavelength) distances from the seismic source is derived. We examine the case where sound speed in the layer higher than in the fluid half-space (this holds antiwaveguide propagation of acoustic waves), and the case of low-velocity layer, when near-surface refraction waveguide occurs. Acoustic waves average by period radiation powers obtained in integral expressions for three different areas of fluid half-space. Numerical analysis of the radiation power is conducted in the case of high-velocity and low-velocity near-surface layers. Results of data processing from field experiments on acoustic and seismic signals detection during industrial explosions in quarry (northwest Russia) presented. Hide Abstract 

Empiric kinematic and dynamic acoustic characteristic of different genotypes rocks and their strength properties interdependence have been consider. Due to the small amount of researching the acoustic quality factor and the strength of rocks interdependencies they receive special attention. It is shown that the smaller value of the acoustic Q-value corresponds to the smaller tensile strength of rock. They are connected with each other. It has been shown on the example of the limestone samples of different lengths the insignificant influence of the scale factor on the interdependence of the acoustic quality factor and residual strength. These dependencies can be used for non-destructive evaluation techniques of the rock strength and resources of underground structures. Hide Abstract 

В работе рассматривается новый метод измерения скоростей продольных и поперечных волн в непрозрачном слое железа в ячейке алмазной наковальни DAC (diamond anvil cell) при высоких давлениях методом лазерного ультразвука LU (laser ultrasonics) в конфигурации «точечный источник - точечный приемник». Главное преимущество метода в конфигурации «точечный источник – точечный излучатель» для непрозрачных аморфных твердых тел и расплавов в том, что не требуется никаких дополнительных данных для измерения упругих свойств твердых тел под давлением (например, сведений о толщине образца под высоким давлением). В данной работе представлены результаты по изучению спектральных особенностей генерации и приема сдвиговых и продольные волн в железе под высоким давлением в LU-DAC установке. Hide Abstract 

In the course of the research was conducted short-term and long-term ultrasonic treatment samples of high viscosity structured oil content of asphaltenes 15-16%. The results of measurements and calculations for short ultrasonic processing of high-viscosity oil show that the rheological dependencies there are intervals of shear rate, showing a decrease or increase in viscosity. Prolonged ultrasonic treatment does not lead to qualitative changes in the colloid-dispersed structure. After ultrasonic treatment of the structured oil can be observed as positive effects (reduced viscosity) and negative effects (increase in viscosity, precipitation, clogging of the pore space of the reservoir). For each case (individual type of oil, reservoir conditions, the power source of ultrasound), it is necessary to determine the appropriate processing time for achieving maximum positive effect.  Hide Abstract 

The movement of liquids and gases through porous environments is accompanied by generation of acoustic fluctuations – filtrational noise. A spectrum of such noises depends on properties of liquids and a porous collector, and also on mode of current. In work results of laboratory experiments on research of spectral characteristics of the filtrational noise generated by a stream of compressed air, filtered through the sample of the porous environment of a real deposit are presented. Design features of experimental equipment and a detail of the conducted research are described. The interrelation of the basic frequencies and amplitudes of generated fluctuations with a current mode is revealed. Visual pictures of a spectrum of filtrational noise are presented. The received results can be used in the decision of identification problems by definition of properties and working intervals of productive layers. Hide Abstract 

Work is directed on increase of efficiency of acoustic influence on well bottom zone for in-crease in oil recovery of a layer. On the basis of the researches spent by authors it is shown that the account of features of distribution of sound fluctuations in the punched chink and a choice of a mode of acoustic influence allows to reduce losses of energy of elastic waves considerably. Processes of distribution of elastic fluctuations in a chink and their transfers through punched apertures in environment are investigated. Settlement formulas for definition of frequency of own fluctuations and good quality in the punched pipe are received. Conditions of maintenance of a resonant mode are defined. Hide Abstract 

The paper presents results of study of the elastic properties of fluid-saturated unconsolidated granular medium (FUGM). As a model of the media we used a system of densely packed metal balls with a diameter of 2 mm and 4 mm, the space between them was filled with liquids with different elastic properties - ethanol, glycerin and mineral motor oil SAE 10W-30. The influence of static (external pressure) and dynamic effects (the amplitude of the probe signal) on the linear and nonlinear elastic properties of FUGM. Linear elastic properties were investigated by pulse method, the nonlinear elastic properties of the medium were investigated by the spectral method. We experimentally investigated dependence of the velocity of elastic waves on the external pressure and the amplitude of the probe signal, and the amplitude of the second harmonic on the amplitude of the signal of fundamental frequency. The results were analyzed on the basis of the Hertz and Biot theory.  Hide Abstract 

Laboratory and field seismoacoustic researches on influence of external statistical and wave indignations on parameters of acoustic radiations from geological environments are conducted. During experiments continuous record and computer processing of the signals of acoustic and seismoacoustic emission (issue) in the mountain environment was carried out. These signals are informative parameters of an intense and deformation condition of the environment and its change, with development of new fields of a jointing and new filtrational fields. Essential influence of a saturating the pore fluid on character and extent of development at the microlevel of the processes of formation of cracks, and also a frequency range of acoustic and seismoacoustic emission in the mountain environment is established. The petrosaturated environment emits during loading less energy in the form of radiation – as if "accumulating" it. This process is followed by formation of abrupt spasmodic metastable states, thus in various temporary scales there are activity cycles at the beginning of which during the short periods of "calm" the system is in nodal points of "bifurcation". In them the further way of evolution of system – or decides on a tendency of increase of orderliness and accumulation of energy, or on increase of a randomness and allocation of internal energy. The received results can become a basis of creation of new highly effective innovative technologies of studying and investigation of a subsoil of Earth, and also seismoacoustic impact on productive layers for the purpose of increase of efficiency of wells and increase in oil recovery of layers. Hide Abstract 

Wave propagation in porous medium containing emulsion is numerically investigated. The two-velocity, two-stress mathematical model of porous medium is used. The power law constitutive relation for emulsion is taken. The viscous friction force and associated mass force are accounted in the interaction force between porous medium and emulsion. The pulse evolution in porous medium saturated with emulsion is calculated. The model parameters of the emulsion are taken from experimental investigations of the other authors. The calculation results on wave evolution are compared with that for the porous medium saturated with water and oil. It is shown that there is a frequency range where wave attenuation in porous medium saturated with emulsion is higher than attenuation in water or oil saturated porous medium. The effective viscosity estimates of the emulsion were made and the dispersion curves for linear waves in the porous medium containing emulsion were analyzed.  Hide Abstract 

Heavy raw oil modules slowly vary in proportion to log of time. The recent research of complex shear module dependence on strain amplitude reveals log time increasing of nonlinear parameter for sample of raw oil. Experiments have been done at the rotation rheometer in the mode of small torsional oscillations. Experiment showed the complex shear module linearly decreases with amplitude of shear excitation increase and that could be if the value of shear module of the oil linearly varies with strain modulus. Results of the first three harmonics amplitudes analysis for visco-elastic response on both amplitude excitation and time are presented as well. Hide Abstract 

With the help of designed experimental device and measurement technique an emission of sound waves (acoustic emission) is discovered and registered during «solid-state combustion» in the mixes of organic crystals. The spektral-correlation analysis of the registered acoustic signals is offered as a new effective method of research of the combustion features caused by the moving of the reacting environment. The processes accompanying combustion are in-situ diagnosed and identified with its help; their space-time distribution in the reacting sample is detailed. The local reaction germs in a green mix and thermal cracking of organic crystals are found out. Dynamics of formation of bubbles and porous structure of products in the reaction front and during their cooling is studied. The moment of changing of chemical reaction mode is established. Correlation between the structure of synthesized condensed products of combustion and peculiarities of acoustic emission is shown. That fact causes principal possibility of acoustic certification of «solid-state combustion» products. Hide Abstract 

The problem of remote estimation of pulse source coordinates using relative delays of the signals accepted by hydrophones of radiobuoys in spaced points is considered. Location coordinates of radiobuoys are defined by GPS/GLONASS navigation with some known error. To decrease the estimation inaccuracy of pulse source coordinates the redefined system of interval equations for four signal receivers is considered. Settlement ratios are made. Configurations of placement of signal receivers when inaccuracies of coordinates are sufficient are defined by mathematical simulation. Mathematical simulation results and results of experiments in shallow water area by remote estimation of pulse source coordinates are given. Hide Abstract 

For determining multimolecular adsorption isotherms of water vapor on the surface of solid surface acoustic waves is proposed to use. It has been shown that the relative change of SAW velocity is proportional to the thickness of the adsorption layer. Therefore, the isotherm of SAW velocity change characterizes the adsorption isotherm of vapor. For the calibration of the vapor adsorption isotherm the original method, based on the determination of the thickness of the adsorbed layer at the zero value of temperature coefficient of delay is proposed to use. Hide Abstract 

Studies of "noise pollution the" of territories which are placed near the railroads or street railway, and also experimental studies of sound fields of local noise zones (race circuit, airports, gunnery range) which were carried out in recent years by the acoustics department employees confirm need of rationing both levels of sound pressure, and oscillatory velocity of medium particles for control of noisiness level at low sound frequencies. Methods of calibration in close field of pressure gradient receivers at the anechoic chamber and real room are discussed. Hide Abstract 

The processes of propagation of phase conjugate ultrasound waves in stationary and moving random media containing micro-inclusions in the form of gas bubbles and solid spheres are studied experimentally and theoretically. Wave phase conjugation at frequency 10 MHz was implemented by the supercritical parametric method. The qualitative difference of the statistical properties of scattered and phase conjugate acoustic fields is established. In contrast with detected stochastic signals of the scattered waves the signals of the phase conjugate waves are regular and more informative for determination of concentrations and parameters of the scatterers. The theoretical model describing observed features of the coherent backscattering of phase conjugate waves is developed. Hide Abstract 

Nowadays, the acoustic waves propagating in isotropic cylindrical waveguides and in waveguides made of piezoelectric ceramics are well studied. It has previously been shown that some compression modes in piezoceramic cylinders have a high electromechanical coupling coefficient, which makes them attractive for creating various acoustoelectronic devices. However the piezoceramics for production of these wave guides must have longitudinal electric polarization that complicates production of long enough wave guides. Fabrication of cylindrical waveguides from piezoelectric crystals, such as lithium niobate, is more technologically. However, there are no directions with axial symmetry in this crystal, so the calculations became more complicated. In this paper we perform the theoretical study of acoustic waves propagating in a cylinder of lithium niobate whose crystallographic Z axis coincides with the axis of the cylinder. To solve this problem, we use the finite element method, which allowed us to determine the natural frequencies of the cylinder. Phase velocities of waves of different orders in the waveguide under study are calculated. Comparison with the results obtained by a semi-analytical method in which material of niobate of lithium assumed the transversely isotropic is carried out. The error to which leads absence of the accounting of anisotropy of material of a wave guide is estimated. The existence of piezoactive acoustic waves with mainly tangential polarization that would be impossible without anisotropy is predicted. Hide Abstract 

The method of estimation of velocity vector of the moving source by using linear antenna and vertical cylindrical antenna is presented. The method is based on the analysis of the dynamics of the broadband spectra of the signals in the interference maxima location. The stability of the method is considered in the case of variation of wave channel transfer function. Hide Abstract 

The simulation of the algorithm for the wideband noise source detection and depth and range estimation in passive mode with the Bartlett matched field processor is performed. Response characteristics of vector-scalar and scalar long-aperture linear arrays are compared. It is shown that robust coordinate estimates are obtained even when accurate waveguide parameters are not known and when there are moderate dynamic perturbations in a water column. It is found that the vector-scalar array has 5 to 10 dB higher signal-to-noise ratio than the scalar one with the same aperture.  Hide Abstract 

The asymptotic solution tasks of normal waves diffraction by elastic thin-walled shells in the inhomogeneous waveguards have been found. The theory of motion of an elastic thin-walled shells Love type have conceded. In the report the scattering field objects are presented in the sum of normal waves these amplitudes, describable the integrals of shell displacements. The closed system of the singular differential equations for shell displacements in the waveguard, these influence external medium, have been found. The task sound shell radiation exited suffers shell forces have conceded. The asymptotic form of the directivity pattern sound radiation of prolate shell of revolution have been found. Keywords: normal waves, theory of shells Love type, singular differential equations, directivity pattern.  Hide Abstract 

Using the theory of adiabatic modes, the problem of low-frequency sound field transverse coherence length estimation is considered analytically for a shallow-water waveguide in the presence of background internal waves. The Garrett-Munk style spectrum modified for a shallow-water environment is exploited to describe vertical displacements of the liquid. Internal wave field is assumed to be isotropic. Explicit dependencies of the coherence length on the source range, sound frequency, energy density of internal waves, and other parameters are obtained. Qualitative and quantitative agreement between analytical estimates and numerical simulation results is demonstrated. The comparison of the transverse coherence length estimates with the experimental data is performed. Hide Abstract 

The paper describes the phenomenon of the electromagnetic and acoustic waves interaction in a solid conductivity medium, and at the water-air reference to problem of radio communication with submarine vehicles. Quantifies the effect of parametric modulation during action of both types of waves. The results of laboratory observations are shown. The ratios to assess the quantitative relationship between the electrical conductivity of water, salt concentration, temperature, acoustic pressure are obtained by means of the kinetic theory of electrolytes. It is shown that the acoustic pressure caused by irradiation with ultrasound solution leads to non-linear dependence of conductivity from its power flux density of the acoustic radiation. The substantiation that the parametric interaction effect of electromagnetic and acoustic fields appears most clearly in the skin layer of the electromagnetic wave in the water surface illumination ultrasound. That can be considered as the effect of heterodyne radio. Hide Abstract 

The analysis is carried out for the low frequency (300±30 Hz) intensity fluctuations of the sound pulses propagating in the shallow water waveguide in the presence of nonlinear internal waves (NIW) in the experiment Shallow Water 2006 (Atlantic shelf of USA). Signals were being received by vertical line array (distance to the source ~20 km). NIW train was placed entirely inside of an acoustic track during time period of the sound radiation. Angle between wave front of NIW and direction of an acoustic track was ~10°. Theoretical modeling of spectrum of fluctuations were obtained using theory of authors for the sound fluctuations due to mode coupling. The main feature of the theory is existence of the so called «predominating frequency», corresponding to the spectral component of maximal amplitude. Comparison of modeling results and experimental data allows us to interpret position of the maximum in the spectrum as predominating frequency. Contribution of horizontal refraction is discussed as well. Hide Abstract 

This paper presents a method of estimating the Doppler shift, which is based on the application of the signal package, consisting of complex signals with "good" autocorrelation properties and operations of autocorrelation (the "convolution" of the received signal with itself) on the receiver. The experimental results validate the approach. Full-scale data obtained are compared with measurements of GPS and similar an acoustic approaches to estimate the Doppler shift. Hide Abstract 

Low-frequency (50 to 300 Hz) sound propagation in shallow water at the range r of 0.3 to 5 km from the source is investigated in numerical experiments. Sea bottom is assumed to be a liquid homogeneous medium. It is compared two cases: where the sound speed in the bottom is higher than the sound speed in the water column, and where it is lower (rigid and soft bottoms). Soft bottom is associated with gas-saturated sediments that are situated in the area of natural gas accumulation. Calculations are performed using the normal mode representation of the sound field. Both propagating and leaky modes (including quasi-modes) are taken into account. Averaged range dependencies of intensity I decay for different frequencies and sound speeds in the bottom are obtained. In the general case, significant deviation from the «3/2 law» (I ~ r^–3/2) is observed. Maximum deviation takes place for a soft bottom. By approximating the obtained intensity decay dependencies with straight lines on a logarithmic scale, waveguide sound attenuation coefficients \beta(tangents of the slopes) are estimated as functions of frequency and sound speed in the bottom. It is demonstrated that the value of \beta increases monotonically with sound speed in a soft bottom and decreases monotonically with sound speed in a rigid bottom. Maximum value of \beta depends on frequency, and it is reached when sound speed in the bottom is close to its value in water.  Hide Abstract 

In this paper the possibility of the sound channel forming by the inhomogeneous distribution of strongly compressible inclusions – gas bubbles in homogeneous water-like media is investigated. The method of calculation of the acoustic field of intense wave beams near the axis of the sound channel is proposed. Field of the intense Gaussian beam is calculated for the case of the mismatch of its axis with the axis of the sound channel. The methods developed can be applied to calculate the intense fields in natural media, such as gas-saturated bottom sediments, and in the built media – metamaterials that let to control the transformation of space-time structure of the field. Hide Abstract 

The problem of correlation between the temporal spectra of the frequency shifts of interference maxima of a sound field and oceanic perturbation has been solved in the adiabatic approximation. The case of wind-induced roughness is considered on the basis of the relationship established. The questions of surface roughness monitoring efficiency are discussed.  Hide Abstract 

In this paper we demonstrate numerically vertical array output of multimodal acoustical signal, which propagates in randomly inhomogeneous oceanic waveguide. The input signal is sum of normal waves with given wave number spectrum and random amplitudes, which have some (range-dependent) scale of cross-modal correlations. We obtain quantitative estimator of impact basic physical signal characteristics (intensity spectrum of the signal-carrying modes, wave number spectrum, cross-modal correlations) on the array output in different oceanic noise models (continuous and discrete mode spectrum). The results of this work enable to find dependence large array efficiency on multimodal signal’s propagation effect in underwater sound channel.  Hide Abstract 

In the Barents Sea in summer-autumn requirements repeatedly per different years (since 1972) an experience on long-range diffusion of explosive and tone signals including of re-search courts of the Institute of Acoustic of Russian Academy of Sciences were put. On ma-terials of these experience the analysis of spatial - energy and time frame of sound fields is conducted, losses of sound energy in ground adjournment are estimated and its frequency dependence, the opportunities of build-up of acoustic model of a bottom compounded with effects of conducted experience are discussed. Hide Abstract 

The investigation of the time variability of the cavitation thresholds of sea water in the three region of the World Ocean is presented. The first region is closed shallow sea gulf, the second region is in open part of Atlantic ocean, the third region is near the coast in region of powerful flow of river water. The made studies show that the time variability of the cavitation thresholds of sea water in the different region of the World Ocean is complex character and apparently connected with the presence of total daily rhythm of physical ,chemical and biological processes in the ocean, particularly, with the tidal phenomena, as well as with the fluctuations discontinuity layer under the action of internal waves.  Hide Abstract 

Results of investigations of hydroacoustic oscillator charateristics on stationary 125-meter track in coastal zone of the Black Sea for two rays conditions of the sea structure are presented. The impact of variability of hydrophysical parameters of environment on mode of operation of oscillator are discussed.Possibility of using the oscillator as a tool for monitoring of the sea medium is discussed.Results of temperature measurements of sea environment by termistor string during oscillator operation is shown.  Hide Abstract 

Results of the test of power parametric array at the marine range of the Hydrophysical research institute in Sukhum (Abkhazia) are presented in the paper. Methods of nonlinear acoustics are discussed for hydrographical research, which appeared when sharp directed wide frequency band acoustical signal from parametric array will be fitted to frequency pattern of the marine waveguide. Results of the research show the single mode marine waveguide excitation by parametric array in the wide frequency band are obtained. The ability to compress the wide frequency band acoustical signal under it propagation due to waveguide dispersion is shown. This compression leads to increase the signal-to-noise ratio. Some aspects of sharp directed parametric array application for hydrographical research at the Black sea and in Arctic are considered as well. Hide Abstract