卷 65, 编号 5 (2019)

In 1678 Huygens formulated a principle postulating that each point on a wave front acts as a point source emitting a spherical wave which travels with a local velocity. The field at a given point some time later is then the sum of the fields of each of these point sources [1]. In this article a numerical method is presented for 2D problems of sound propagation and scattering, conforming that physical assumptions.

In this article, an acoustic energy harvester (AEH) is conceptualized, designed, fabricated and tested. The developed AEH (DAEH) consists of two Helmholtz cavities (HCs) and a commercially available piezoelement. The HCs were fabricated from Teflon material using conventional machining operations. An indigenous test bench for in-lab characterization of DAEH has also been developed. Various experiments were performed to experimentally record the frequency response function, loading and power characteristics. Additionally, the in-lab and open-air characterization of the DAEH is also reported. Furthermore, the proposed prototype of DAEH is compared on the basis of various benchmarks with the prototypes available in the literature. The experimental results indicate a maximum power density of 32.7 μW/cm³ at 130 dB.

A method is proposed for removing heat from the transducer of an acousto-optic deflector without substantial acoustic damping. The rear surface of the transducer and the heat–radiator surface are kept in contact through a thin sound-insulating fluid layer. The method is based on the considerable difference in the complex acoustic impedances for shear vibrations of fluids and a solid (the piezotransducer) by means of efficient heat transfer through the fluid. In the experiment, a continuous operation mode of the acousto-optic deflector is achieved with an acoustic wave intensity of more than 20 W/cm². The acousto-optic deflector has been created that operates in the Bragg diffraction mode with a phase–modulation index of 3π with an input continuous controlling electric power of 3 W. The deflector characteristics for a light wavelength of 1.06 μm are as follows: diffraction efficiency no less than 90% in the 25 MHz frequency band at an absolute scanning angle of 40 mrad.

Real recordings of bowhead whale signals and numerical simulation were used to investigate the propagation of such signals in an Arctic-type shallow-water waveguide. The authors analyzed attenuation and distortion of whale signals with increasing distance in the following conditions: (1) a soft and hard bottom, (2) different whale depths, (3) surface waves, (4) additive noise, and (5) reception by a single hydrophone and a vertical array. Signal attenuation was estimated by the change in sound pressure level (SPL). Signal distortion was estimated by the change in the correlation coefficient for the spectrograms of received signals and the reference spectrograms. It is shown that, compared to signals from a single receiver, the attenuation and distortion characteristics of the array output signals are more stable and resistant to changes in whale depth, to possible, under Arctic conditions, significant variations in sound speed in the bottom along the acoustic path, and to the effects of additive noise. The results can be used for passive monitoring of bowhead whales on the Arctic shelf.

The paper presents the acoustic communication equipment with bottom stations of the Shelf-2014 hydroacoustic complex—built-in acoustic bottom station modems and a portable telecommand unit. The main technical solutions adopted in the development process and confirmed by a number of experiments are described. The results of operation of the equipment under marine conditions are considered, and ways of further development are outlined.

The article discusses the results of experiments conducted in September 2017 to prove the applicability of positioning underwater objects during their operation at depths substantially exceeding the depth of the underwater sound channel axis. The authors present results of experimental studies and numerical analysis of the effect of focusing of the acoustic energy in the near-bottom layer on the shelf and its transition into deep-water (up to 500 m) layers of the Sea of Japan for summer–autumn hydrological conditions. Experiments on reception of broadband pulsed signals with a center frequency of 400 Hz were carried out at various distances (20, 68, 86, 90, and 198 km) from a source of navigation signals moored at a depth of 35 m at the shoreline near Cape Schulz. The receiving of acoustic signals was performed by a system of distributed over depth up to 500 meters hydrophones, with the possibility of long-term signal recording at fixed depths and during submergence. The experimental results allowed to study the impulse responses of acoustic waveguides, and estimate the effective propagation velocities of navigation signals received at different depths, and to draw conclusions about the possibility of solving positioning problems for autonomous underwater vehicles at depths up to 500 m and distances up to 200 km from the source of navigation signals. Mathematical modeling of acoustic wave propagation in a waveguide reproducing the experimental conditions by the normal mode technique was also carried out.

In 2015, during seismic surveys on the northeast shelf of Sakhalin Island, measurements of acoustic pressure were conducted near the sea floor at preset monitoring locations positioned both within and at the edge of the summer-autumn feeding grounds of the Western gray whales. Forty Autonomous Underwater Acoustic Recorders (AUARs) were used for this monitoring, the measurements had a bandwidth of 2–15 000 Hz and a dynamic range of 145 dB; the total duration of these acoustic measurements was 4312 days. The objective of the monitoring presented in this article was to analyze the characteristics of acoustic pulses generated on the shelf by seismic sources and onshore foundation pile driving for multivariate analysis of the effect of these operations on the behavior of western gray whales.

The classical algorithm for localizing noise sources using a planar microphone array is generalized to the case of its application to dipole-type sources. The developed algorithm was verified and validated via data processing of experimental studies of cylinder flow noise and jet–plate interaction noise. We compare the results of localizing dipole noise sources using a planar microphone array employing the developed algorithm and an azimuthal array based on the azimuthal decomposition technique.

In this paper, an explosion experiment was carried out on the OD1219mm-X90-12Mpa natural gas pipeline to study the vibration hazard. Based on a series of experiments, the spatial distribution of the vibration energy was studied. The vibration distribution field was drawn by interpolation method based on re-harmonic equation and it was found that the field was non-circular symmetry. Through in-depth research, it was preliminarily proved that the vibration field had interference characteristics, which was caused by the special vibration source of the pipeline explosion. There was a significant difference in the frequency components between the interference strengthened region and the weakened region. The results shown that the strengthening effect of the interference in the 90° and 30° direction should be taken into account when evaluating the damage scope of the explosion accident. Research provided reference for safety design of parallel pipelines and buildings.

The article presents the results of field tests of marine seismic sources and seismoacoustic areal measuring systems based on autonomous embedded buoys in Lake Ladoga under ice conditions. The authors demonstrate the possibility of separating in the received signal individual modes propagating in the ice cover–water layer–sediment layer–elastic half-space system. An iterative tomographic scheme is proposed that makes it possible to reconstruct high-contrast high-speed anomalies in the considered layered medium. The results of tomographic estimation of the bottom, water layer, and ice layer characteristics in the active mode are presented.

New technologies for the digital recording of broadband complex signals have made it possible to develop and create laboratory autonomous multichannel equipment to record bioacoustic activity on a digital medium with low power consumption and the possibility of continuous recording for up to 4 h. The equipment operates under the control of a fit-PC computer with the Windows operating system and the PowerGraph program for digital recording in a frequency band of the analog path of up to 600 kHz. Equipment testing recorded paradoxical signals from toothed whales with a frequency band exceeding 200 kHz. Signals with an extended frequency band were recorded in a laboratory experiment in open water while solving the problem of target tracking and in an experiment with provocation of acoustic communication behavior.

The paper presents the results of numerical two-dimensional modeling of Rayleigh wave propagation along the curvilinear boundary of a solid ideal medium with a contrasting inclusion. It is shown that ignoring the influence of both a convex and concave relief when interpreting microseismic sounding data can lead to errors for a wide range of reliefs and contrast between an inclusion and the surrounding medium; additional corrections during data processing make it possible to account for or even eliminate these errors in the entire considered parameter range.