scholarly journals SHALLOW WATERS INTERFERENCE PATTERN FEATURES AND APPLICATIONS

2015 ◽  
Vol 33 (3) ◽  
pp. 523
Author(s):  
Antonio Hugo Saroldi Chaves ◽  
Kleber Pessek ◽  
Luiz Gallisa Guimarães ◽  
Carlos Eduardo Parente
Keyword(s):  
Interference Pattern ◽  
Processing Time ◽  
Shallow Waters ◽  
Underwater Sound ◽  
Geoacoustic Inversion ◽  
High Frequencies ◽  
Active Sonar ◽  
Wave Interference ◽  
Invariant Parameter ◽  
Frequency Distance

ABSTRACT. Studies in shallow waters pointed out that the acoustic wave interference patterns have potential application in a broad range of problems in underwater acoustics such as: passive sonar, active sonar, array processing, time-reverse mirrors and geoacoustic inversion. For shallow waters underwater sound waveguides, the main features of this research is interference pattern or “striations” obtained by means of Frequency-time or Frequency-distance spectrograms. This work aims to characterize these interference pattern or striations related to “invariant” parameter β. The theory is developed based on real underwater waveguide. The present results confirm that the parameter β is frequency dependent and at high frequencies it tends to the unity. In another words, far from the waveguide cut-off frequency the present real waveguides could be treated by an ideal waveguide. Besides, in this approximation it is possible to make source-receiver passive distance predictions based on the related interference pattern.Keywords: underwater acoustic, waveguide, interference pattern.RESUMO. Estudos em águas rasas apontam que os padrões de interferência de ondas acústicas têm aplicação potencial em uma ampla gama de problemas de acústica submarina, tais como: sonar passivo, sonar ativo, processamento de arrays, espelhos de reversão temporal e inversão geoacústica. O foco principal desta pesquisa é o padrão de interferência ou estrias obtidas por meio de espectrogramas e gráficos no plano de Frequências e Distâncias. Este trabalho tem como objetivo caracterizar estes padrões de interferência ou estrias com o parâmetro invariante β. A teoria é desenvolvida com base em um guia de onda real. Os resultados deste estudo confirmam que o parâmetro β é dependente da frequência e, em altas frequências, tende à unidade. Em outras palavras, longe da frequência de corte, o comportamento do guia de onda real é semelhante ao guia de onda ideal. Além disso, nesta aproximação, é possível fazer previsões de distância passiva entre o receptor e a fonte com base no padrão de interferência.Palavras-chave: acústica submarina, guia de ondas, padrão de interferência.

SHALLOW WATERS INTERFERENCE PATTERN FEATURES AND APPLICATIONS

2016 ◽  
Vol 33 (3) ◽  
Author(s):  
Antonio Hugo Saroldi Chaves ◽  
Kleber Pessek ◽  
Luiz Gallisa Guimarães ◽  
Carlos Eduardo Parente
Keyword(s):  
Acoustic Wave ◽  
Interference Pattern ◽  
Potential Application ◽  
Underwater Acoustics ◽  
Shallow Waters ◽  
Wave Interference

ABSTRACT. Studies in shallow waters pointed out that the acoustic wave interference patterns have potential application in a broad range of problems in underwater acoustics... RESUMO. Estudos em águas rasas apontam que os padrões de interferência de ondas acústicas têm aplicação potencial em uma ampla gama de problemas de acústica...

scholarly journals Ship noise in an urban estuary extends to frequencies used for echolocation by endangered killer whales

2015 ◽  
Author(s):  
Scott Veirs ◽  
Val Veirs ◽  
Jason D Wood
Keyword(s):  
Transmission Loss ◽  
Source Spectrum ◽  
Automatic Identification ◽  
Identification System ◽  
Underwater Sound ◽  
Killer Whales ◽  
Noise Sources ◽  
Low Frequencies ◽  
High Frequencies ◽  
Location Data

Combining calibrated hydrophone measurements with vessel location data from the Automatic Identification System, we estimate underwater sound pressure levels for 1,582 unique ships that transited the core critical habitat of the endangered Southern Resident killer whales during 28 months between March, 2011, and October, 2013. Median received spectrum levels of noise from 2,812 isolated transits are elevated relative to median background levels not only at low frequencies (20-30 dB re 1 μPa2/Hz from 100-1000 Hz), but also at high frequencies (5-13 dB re 1 μPa2/Hz from 10,000-96,000 Hz). Thus, noise received from ships at ranges less than 3 km extends to frequencies used by odontocetes like the southern resident killer whales for communication and echolocation. Broadband received levels (11.5-40,000 Hz) near the shoreline in Haro Strait (WA, USA) for the entire ship population were 111 ± 6 dB re 1 μPa on average. Mean ship speed was 14.4 ± 4.1 knots. Most ship classes show a linear relationship between received level and speed with a slope near +1 dB/knot. Assuming near-spherical spreading based on a transmission loss experiment we compute mean broadband source levels for the ship population of 173 ± 7 dB re 1 μPa @ 1 m without accounting for frequency-dependent absorption. Spectrum, 1/12- octave, and 1/3-octave source levels for the whole population have median values that are comparable to previous measurements and models at most frequencies, but for select studies may be relatively low below 200 Hz and high above 20,000 Hz. Median source spectrum levels peak near 50 Hz for all 12 ship classes, have a maximum of 159 dB re 1 μPa2/Hz @ 1 m for container ships, and vary between classes by about 25 dB re 1 μPa2/Hz @ 1 m at low frequencies (50 Hz), 13 dB re 1 μPa2/Hz @ 1 m at mid-frequencies (1,000 Hz), and 5 dB re 1 μPa2/Hz @ 1 m at high frequencies (10,000 Hz). Below 200 Hz, the class-specific median spectrum levels bifurcate with large commercial ships grouping as higher power noise sources. Within all ship classes spectrum levels vary more at low frequencies than at high frequencies, and the degree of variability is almost halved for classes that have smaller speed standard deviations.

scholarly journals Ship noise extends to frequencies used for echolocation by endangered killer whales

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e1657 ◽  
Author(s):  
Scott Veirs ◽  
Val Veirs ◽  
Jason D. Wood
Keyword(s):  
Transmission Loss ◽  
Source Spectrum ◽  
Automatic Identification ◽  
Identification System ◽  
Underwater Sound ◽  
Killer Whales ◽  
Noise Sources ◽  
Low Frequencies ◽  
High Frequencies ◽  
Location Data

Combining calibrated hydrophone measurements with vessel location data from the Automatic Identification System, we estimate underwater sound pressure levels for 1,582 unique ships that transited the core critical habitat of the endangered Southern Resident killer whales during 28 months between March, 2011, and October, 2013. Median received spectrum levels of noise from 2,809 isolated transits are elevated relative to median background levels not only at low frequencies (20–30 dB re 1 µPa2/Hz from 100 to 1,000 Hz), but also at high frequencies (5–13 dB from 10,000 to 96,000 Hz). Thus, noise received from ships at ranges less than 3 km extends to frequencies used by odontocetes. Broadband received levels (11.5–40,000 Hz) near the shoreline in Haro Strait (WA, USA) for the entire ship population were 110 ± 7 dB re 1 µPa on average. Assuming near-spherical spreading based on a transmission loss experiment we compute mean broadband source levels for the ship population of 173 ± 7 dB re 1 µPa 1 m without accounting for frequency-dependent absorption. Mean ship speed was 7.3 ± 2.0 m/s (14.1 ± 3.9 knots). Most ship classes show a linear relationship between source level and speed with a slope near +2 dB per m/s (+1 dB/knot). Spectrum, 1/12-octave, and 1/3-octave source levels for the whole population have median values that are comparable to previous measurements and models at most frequencies, but for select studies may be relatively low below 200 Hz and high above 20,000 Hz. Median source spectrum levels peak near 50 Hz for all 12 ship classes, have a maximum of 159 dB re 1 µPa2/Hz @ 1 m for container ships, and vary between classes. Below 200 Hz, the class-specific median spectrum levels bifurcate with large commercial ships grouping as higher power noise sources. Within all ship classes spectrum levels vary more at low frequencies than at high frequencies, and the degree of variability is almost halved for classes that have smaller speed standard deviations. This is the first study to present source spectra for populations of different ship classes operating in coastal habitats, including at higher frequencies used by killer whales for both communication and echolocation.

Relationship between Boreal Summer Circulation Trend and Destructive Stationary-Transient Wave Interference in the Western Hemisphere

2021 ◽  
pp. 1-38
Author(s):  
Dong Wan Kim ◽  
Sukyoung Lee
Keyword(s):  
Interference Pattern ◽  
Western Hemisphere ◽  
Boreal Summer ◽  
North American Monsoon ◽  
Destructive Interference ◽  
Latent Heating ◽  
Eastern Canada ◽  
Transient Wave ◽  
The North ◽  
Wave Interference

AbstractThis study examines the role of the latent heating in exciting the upper-level circulation anomaly which destructively interferes with the climatological stationary wave in the Western Hemisphere during boreal summer. This destructive interference pattern closely resembles the circulation trend which is known to be responsible for surface heat extreme trends. To investigate the mechanism behind this circulation anomaly, daily stationary-transient wave interference and related meteorological variables are analyzed using reanalysis data for the period of 1979-2017. Numerical model simulations forced by reanalysis heating anomalies indicate that the destructive interference pattern is most effectively excited by latent heating anomalies over the North Pacific and eastern Canada. The North Pacific heating anomaly drives circulation anomalies that not only resemble the destructive interference pattern, but also transport moisture into eastern Canada. The resulting latent heating over eastern Canada drives circulation that further reinforces the destructive interference pattern which includes a prominent high pressure system over Greenland. Tropical heating also plays a role in driving the destructive interference pattern. On intraseasonal time scales, the destructive interference pattern is preceded by suppressed Indo-western Pacific heating and enhanced North American monsoon heating. On decadal time scales, both heating centers have strengthened, but the trend of the North American monsoon heating was greater than that of the Indo-Western Pacific heating. These uneven heating trends help explain the resemblance between the destructive interference pattern and the circulation trend over the Western Hemisphere.

scholarly journals AN ANALOG FLUID MODEL FOR SOME TACHYONIC EFFECTS IN FIELD THEORY

2011 ◽  
Vol 26 (31) ◽  
pp. 2335-2344 ◽  
Author(s):  
E. ARIAS ◽  
C. H. G. BÉSSA ◽  
N. F. SVAITER
Keyword(s):  
Field Theory ◽  
Interference Pattern ◽  
Fluid Model ◽  
Sound Radiation ◽  
Wave Interference ◽  
Classical Wave

We consider the sound radiation from an acoustic point-like source moving along a supersonic ("space-like") trajectory in a fluid at rest. We call it an acoustic "tachyonic" source. We describe the radiation emitted by this supersonic source. After quantizing the acoustic perturbations, we present the distribution of phonons generated by this classical tachyonic source and the classical wave interference pattern.

Wave interference pattern from the wings of a bee

1990 ◽  
Vol 28 (5) ◽  
pp. 335-335
Author(s):  
David R. Lapp
Keyword(s):  
Interference Pattern ◽  
Wave Interference

scholarly journals Ship noise in an urban estuary extends to frequencies used for echolocation by endangered killer whales

2015 ◽  
Author(s):  
Scott Veirs ◽  
Val Veirs ◽  
Jason D Wood
Keyword(s):  
Transmission Loss ◽  
Source Spectrum ◽  
Automatic Identification ◽  
Identification System ◽  
Underwater Sound ◽  
Killer Whales ◽  
Noise Sources ◽  
Low Frequencies ◽  
High Frequencies ◽  
Location Data

Combining calibrated hydrophone measurements with vessel location data from the Automatic Identification System, we estimate underwater sound pressure levels for 1,582 unique ships that transited the core critical habitat of the endangered Southern Resident killer whales during 28 months between March, 2011, and October, 2013. Median received spectrum levels of noise from 2,812 isolated transits are elevated relative to median background levels not only at low frequencies (20-30 dB re 1 microPa2/Hz from 100-1000 Hz), but also at high frequencies (5-13 dB re 1 microPa2/Hz from 10,000-96,000 Hz). Thus, noise received from ships at ranges less than 3 km extends to frequencies used by odontocetes like the Southern Resident orcas for communication and echolocation. Broadband received levels (20-96,000 Hz) near the shoreline in Haro Strait (WA, USA) for the entire ship population were 111 +/- 6 dB re 1 microPa on average. Mean ship speed was 14.4 +/- 4.1 knots. Most ship classes show a linear relationship between received level and speed with a slope near +1 dB/knot. Assuming near-spherical spreading based on a transmission loss experiment, we compute mean broadband source levels for the ship population of 173 +/- 7 dB re 1 microPa @ 1 m without accounting for frequency-dependent absorption, and 178 +/- 13 dB re 1 microPa @ 1 m with absorption. Spectrum, 1/12-octave, and 1/3-octave source levels for the whole population have median values that are comparable to previous measurements and models at most frequencies, but for select studies may be relatively low below 200 Hz and high above 20,000 Hz. Median source spectrum levels (without accounting for absorption) peak near 50 Hz for all 12 ship classes, have a maximum of 159 dB re 1 microPa2/Hz @ 1 m for container ships, and vary between classes by about 25 dB re 1 microPa2/Hz @ 1 m at low frequencies (50 Hz), 13 dB re 1 microPa2/Hz @ 1 m at mid-frequencies (1,000 Hz), and 5 dB re 1 microPa2/Hz @ 1 m at high frequencies (10,000 Hz). Below 200 Hz, the class-specific median spectrum levels bifurcate with large commercial ships grouping as higher power noise sources. Within all ship classes spectrum levels vary more at low frequencies than at high frequencies, and the degree of variability is almost halved for classes that have smaller speed standard deviations.

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