scholarly journals Analysis of Flame Suppression Capabilities Using Low-Frequency Acoustic Waves and Frequency Sweeping Techniques

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1299
Author(s):  
Jacek Łukasz Wilk-Jakubowski
Keyword(s):  
Acoustic Waves ◽  
Low Frequency ◽  
Fire Detection ◽  
Acoustic Method ◽  
Acoustic Signals ◽  
Fast Response ◽  
Measurement Results ◽  
Flame Suppression ◽  
Flame Detection ◽  
Frequency Sweeping

Symmetry plays a key role in the processing and analysis of not only visual but also acoustic signals in various multidisciplinary areas. New innovative and environmentally friendly methods for extinguishing flames are still being sought worldwide. One of these techniques appears to be the acoustic method. A laboratory stand was built for this purpose, which was coupled with the tested prototype of a high-power acoustic extinguisher, and then the original experiments and analyses of extinguishing effectiveness were carried out. For extinguishing, waveforms with specified parameters selected symmetrically around the frequency for which the extinguisher was designed were used. The aim of this article is to present and discuss selected measurement results concerning the possibility of flame extinguishing with the use of sinusoidal acoustic waves of low frequency (below 21 Hz), as well as with the use of frequency sweeping techniques with set parameters. Such an extinguisher can be equipped with an intelligent module so that the extinguisher may be activated automatically (without human intervention) when flames are detected. The benefits of this combination as well as the importance of image processing for flame detection are also presented in this paper. This solution, with its good fire detection and fast response, may be applicable for extinguishing firebreaks in particular.

scholarly journals Investigation of the channel for information transfer by electric, electromagnetic and acoustic waves in layered environment with ice cover

2020 ◽  
Vol 196 ◽  
pp. 02014
Author(s):  
Vladimir Korochentsev ◽  
Vey Syue ◽  
Viktor Petrosyants ◽  
Artem Em ◽  
Ivan Garasev ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Electromagnetic Wave ◽  
Acoustic Waves ◽  
Electromagnetic Waves ◽  
Information Transfer ◽  
Electromagnetic Wave Propagation ◽  
Low Frequency ◽  
Acoustic Signals ◽  
Half Wave ◽  
To Receive

A theoretical model of electromagnetic wave propagation in an ice layer was developed. A half-wave vibrator frozen in an ice layer is used as a receiving-radiating system of electromagnetic waves. Schemes of developed acoustic low-frequency radiators based on electric sparks are described. The possibility of application of the developed systems to receive acoustic signals from earthquake ice source is under discussion.

Fish Attraction with Pulsed Low-Frequency Sound

1968 ◽  
Vol 25 (7) ◽  
pp. 1441-1452 ◽  
Author(s):  
Joseph D. Richard
Keyword(s):  
Acoustic Stimulus ◽  
Low Frequency ◽  
Reef Fishes ◽  
Test Site ◽  
Acoustic Signals ◽  
Commercial Fisheries ◽  
Test Results ◽  
Potential Applications ◽  
Predatory Fishes ◽  
Underwater Television

A series of tests were conducted to determine the effectiveness of pulsed low-frequency acoustic signals for attracting fishes. The acoustic signals were contrived to simulate the hydrodynamically generated disturbances normally associated with active predation. Underwater television was used to observe fish arrivals during both control and test periods. Demersal predatory fishes were successfully attracted although they habituated rapidly to the acoustic stimulus. Members of the families Serranidae, Lutjanidae, and Pomadasyidae were particularly well represented among the fishes attracted. Sharks were also attracted in considerable numbers. Herbivorous reef fishes, although common around the test site, were not attracted. Possible relationships between the test results and the hearing capabilities of fishes are discussed. It is concluded that acoustic attraction techniques have potential applications in certain existing commercial fisheries.

Modelling the effects of distance on the probability of fire detection from lookouts

2006 ◽  
Vol 15 (2) ◽  
pp. 197 ◽  
Author(s):  
Francisco Castro Rego ◽  
Filipe Xavier Catry
Keyword(s):  
Forest Fires ◽  
Detection System ◽  
Fire Detection ◽  
Fast Response ◽  
Fire Loss ◽  
Detection Function ◽  
Related Factors ◽  
New Approach ◽  
Forest Fire Management ◽  
In Fire

In the management of forest fires, early detection and fast response are known to be the two major actions that limit both fire loss and fire-associated costs. There are several inter-related factors that are crucial in producing an efficient fire detection system: the strategic placement and networking of lookout towers, the knowledge of the fire detection radius for lookout observers at a given location and the ability to produce visibility maps. This study proposes a new methodology in the field of forest fire management, using the widely accepted Fire Detection Function Model to evaluate the effect of distance and other variables on the probability that an object is detected by an observer. In spite of the known variability, the model seems robust when applied to a wide variety of situations, and the results obtained for the effective detection radius (13.4 km for poor conditions and 20.6 km for good conditions) are in general agreement with those proposed by other authors. We encourage the application of the new approach in the evaluation or planning of lookout networks, in addition to other integrated systems used in fire detection.

scholarly journals Analysis of Propagation and Distribution Characteristics of Leakage Acoustic Waves in Water Supply Pipelines

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5450
Author(s):  
Yunfei Li ◽  
Yang Zhou ◽  
Ming Fu ◽  
Fan Zhou ◽  
Zhaozhao Chi ◽  
...  
Keyword(s):  
Acoustic Wave ◽  
Water Supply ◽  
Acoustic Waves ◽  
Simulation Analysis ◽  
Acoustic Signals ◽  
Detection Methods ◽  
Acoustic Analogy ◽  
Acoustic Wave Propagation ◽  
Source Characteristics ◽  
Water Supply Pipeline

Leakage detection methods based on the analysis of leakage acoustic signals provide an effective technical approach for detecting small leaks in water supply pipelines. From a technical perspective, the study of the propagation characteristics of acoustic waves generated by the leakage in the water supply pipeline is necessary for detecting the leak location on the basis of acoustic signals. In this study, a 3D transient leakage acoustic wave propagation equation was derived by combining the principles of fluid dynamics and Lighthill acoustic analogy theory. The propagation of the leakage-induced noise in water supply pipeline was modelled theoretically. We simulated the propagation of a leakage acoustic wave under different conditions for different target scenarios encountered in actual pipeline inspections. Specifically, we analysed the effect of different factors, such as the pipe size and acoustic source characteristics, on acoustic propagation. Finally, the simulated experiments were practically performed using a self-designed simulated water supply pipeline and self-developed spherical water supply pipeline detector to validate the simulation analysis. The results of this study provide a theoretical guidance and basis for the analysis of characteristics of leakage acoustic wave signals and the recognition of leakage conditions in water supply pipelines.

Studies on the interaction of low‐frequency acoustic signals with the ocean bottom

Geophysics ◽  
1979 ◽  
Vol 44 (12) ◽  
pp. 1922-1940 ◽  
Author(s):  
Salvatore R. Santaniello ◽  
Frederick R. DiNapoli ◽  
Robert K. Dullea ◽  
Peter D. Herstein
Keyword(s):  
Acoustic Waves ◽  
Grazing Angle ◽  
Low Frequency ◽  
Propagation Loss ◽  
Ocean Bottom ◽  
Computer Technique ◽  
Quantitative Evidence ◽  
Ocean Sediment ◽  
Wave Models ◽  
Processing Techniques

Understanding the mechanisms by which the ocean sediment redirects impinging sound back into the ocean is necessary in developing propagation models for sonar performance prediction. The Naval Underwater Systems Center (NUSC) has (1) conducted controlled, self‐calibrating acoustic measurements where the ocean bottom interacted signal is isolated in time for analysis, (2) developed deconvolution processing techniques to aid in describing the impulse response of the ocean sediment, and (3) performed modeling to study the interaction of acoustic waves at the ocean bottom. This paper presents a synopsis of studies showing the necessity of considering the refraction of sound by the ocean sediment when predicting low‐frequency propagation loss. Constructive interference between nonplanar wave sediment refracted sound and sound reflected by the ocean‐sediment interface and subbottom layering can cause negative values of bottom loss when using plane‐wave models to interpret measured data. These models cannot account for all possible acoustic arrivals at a receiver. In addition, for a given frequency and constant ocean bottom grazing angle, bottom loss can be dependent upon both processing bandwidth and source/receiver depth. Deconvolution has aided in time resolution of signals that make up the bottom‐interacted signals. Resolution of these signals aids in interpreting results. A modeling effort utilizing the Fast Field Program (a computer technique for evaluating the field integral by the fast Fourier transform) provides quantitative evidence for the necessity of accounting for the refraction of sound by subocean sediments to interpret properly low‐frequency propagation loss measurements.

scholarly journals Audibility within and Outside Deposited Snow

1985 ◽  
Vol 31 (108) ◽  
pp. 136-142 ◽  
Author(s):  
Jerome B. Johnson
Keyword(s):  
Acoustic Impedance ◽  
Acoustic Waves ◽  
Transmission Loss ◽  
Acoustic Noise ◽  
Acoustic Signals ◽  
Strong Absorption ◽  
Snow Surface ◽  
Subjective Awareness

AbstractFactors which control the audibility within and outside deposited snow are described and applied to explain the preferential detection of sound by persons buried under avalanche debris as compared to persons on the overlying snow surface. Strong attenuation of acoustic waves in snow and the small acoustic impedance differences between snow and air are responsible for the strong absorption and transmission-loss characteristics that are observed for snow. The absorption and transmission-loss characteristics are independent of the direction of propagation of acoustic signals through the snow. The preferential detection of sound by a person buried under snow can be explained by the relatively higher level of background acoustic noise that exists for persons above the snow surface as compared to an avalanche burial victim. This noise masks sound transmitted to persons on the snow surface, causing a reduction of hearing senstitivity as compared to the burial victim. Additionally, the listening concentration of a buried individual is generally greater than for persons working on the snow surface, increasing their subjective awareness of sound.

LOW-FREQUENCY ACOUSTIC SCATTERING BY AN INHOMOGENEOUS MEDIUM

2005 ◽  
Vol 15 (10) ◽  
pp. 1459-1468 ◽  
Author(s):  
GEORGE VENKOV
Keyword(s):  
Refractive Index ◽  
Plane Wave ◽  
Inhomogeneous Medium ◽  
Acoustic Waves ◽  
Spherical Wave ◽  
Low Frequency ◽  
Far Field ◽  
Scattering Medium ◽  
Wave Incidence ◽  
Plane Wave Incidence

This paper deals with the scattering of time-harmonic acoustic waves by inhomogeneous medium. We study the problem to recover the near and the far field using a priori information about the refractive index and the support of inhomogeneity. The incident spherical wave is modified in such a way as to recover the plane wave incidence when the source point approaches infinity. Applying the low-frequency expansions, the scattering medium problem is reduced to a sequence of potential problems for the approximation coefficients in the presence of a monopole singularity located at the source of incidence. Complete expansions for the integral representation formula in the near field as well as for the scattering amplitude in the far field are provided. The method is applied to the case of a spherical region of inhomogeneity and a radial dependent refractive index. As the point singularity tends to infinity, the relative results recover the scattering medium problem for plane wave incidence.

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