The roles of density, geometry, and short‐range positional order in low‐frequency acoustic scattering from fish schools

2006 ◽  
Vol 119 (5) ◽  
pp. 3436-3436
Author(s):  
Thomas R. Hahn ◽  
Tanos Elfouhaily
Keyword(s):  
Short Range ◽  
Acoustic Scattering ◽  
Low Frequency ◽  
Fish Schools

The low‐frequency scattering action of fish schools

1994 ◽  
Vol 95 (5) ◽  
pp. 3020-3020
Author(s):  
Joel Garrelick ◽  
Miguel C. Junger ◽  
Mary L. Lamberton
Keyword(s):  
Low Frequency ◽  
Fish Schools

scholarly journals Simulation and analysis on low-frequency scattering characteristics of the finite cylindrical shell in shallow water

2019 ◽  
Vol 283 ◽  
pp. 03007
Author(s):  
Jinyu Li ◽  
Dejiang Shang ◽  
Yan Xiao
Keyword(s):  
Cylindrical Shell ◽  
Free Space ◽  
Acoustic Scattering ◽  
Low Frequency ◽  
Target Strength ◽  
Wave Direction ◽  
Scattering Field ◽  
Simulation Results ◽  
Finite Cylindrical Shell ◽  
Target Locations

Low-frequency acoustic scatterings from a finite cylindrical shell are numerically analyzed by FEM. The simulation results show that the acoustic-scattering field in waveguide has lots of frequency-related sidelobes, while no sidelobes exist in free space at low frequencies. The simulation also indicates that the module value in waveguide can be almost 20 dB larger than that in free space at low frequency, which is caused by the ocean boundaries. We also demonstrate that when the incident wave direction is normal to the target at low frequency, the target strength will be maximum and the distribution of the acoustic-scattering field is axisymmetric about the incident waving direction. Meanwhile, the acoustic-scattering field is also related to the impedance of the seabed, and the change of the impedance makes just a little contribution to the scattering field. Finally, the influence of different target locations is analyzed, including the targets near the sea surface, seabed and the middle region of the ocean waveguide, respectively. From simulation results, it is evident that the distribution of the acoustic-scattering field at low frequency has a little difference, which is smaller than 0.5 dB with various target locations, and the change is frequency and boundary-related.

scholarly journals Low frequency scattering from fish schools: A comparison of two models

2014 ◽  
Author(s):  
Maria P. Raveau ◽  
Christopher Feuillade
Keyword(s):  
Low Frequency ◽  
Fish Schools

Vibratory communication signal produced by male western conifer seed bugs (Hemiptera: Coreidae)

2008 ◽  
Vol 140 (2) ◽  
pp. 174-183
Author(s):  
Stephen Takács ◽  
Karl Hardin ◽  
Gerhard Gries ◽  
Ward Strong ◽  
Robb Bennett
Keyword(s):  
Short Range ◽  
Field Experiments ◽  
Lodgepole Pine ◽  
Low Frequency ◽  
Wide Band ◽  
Communication Signal ◽  
Vibratory Signal ◽  
Conifer Seed ◽  
Membrane Type ◽  
Piezoelectric Devices

AbstractWe tested the hypothesis that the western conifer seed bug, Leptoglossus occidentalis Heidemann, uses a substrate-borne vibratory signal for short-range communication. To record such a signal we used computers equipped with data-acquisition hardware and software, microphones sensitive to sonic and (or) ultrasonic frequencies, membrane-type and piezoelectric speakers capable of emitting sonic and ultrasonic sound, and piezoelectric devices capable of emitting low-level, low-frequency vibrations. By tapping their abdomen on substrate, males produced a wide-band vibratory signal 20 dB (sound pressure level; 0 dB = 20 µPa) above ambient sound, with dominant frequencies of 115 ± 10 and 175 ± 15 Hz and a distinct temporal pattern. There was no evidence for (i) ultrasonic signal components; (ii) signals produced by females or nymphs, or (iii) repeated trains of signal pulses. In two-choice arena experiments, males and females preferred the played-back recording of the male-produced substrate-borne signal over silent controls, whereas nymphs showed no preference for either stimulus. In two-choice dowel experiments with hickory wood or lodgepole pine crossbeams, females (unlike males or nymphs) preferred played-back recordings of the same signal over controls. In two-choice field experiments, this signal emitted in the air by piezoelectric devices or transferred through a wire to lodgepole pine branches attracted more L. occidentalis than did silent controls. Our data support the hypothesis that L. occidentalis uses a substrate-borne vibratory signal for short-range communication. The use of such a signal is consistent with reports on communication by other true bug species.

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