Herring-eating killer whales debilitate herring with underwater tail slaps and likely herd herring into tighter schools using a feeding-specific low-frequency pulsed call ('herding' call). Feeding on herring may be dependent upon daylight, as the whales use their white underside to help herd herring; however, feeding at night has not been investigated. The production of feeding-specific sounds ...

The interdisciplinary field of assessing the impacts sound on marine life has benefited largely from advancement underwater acoustics that occurred after World War II. Acoustic parameters widely used in were redefined to quantify levels relevant animal audiometric variables, both at source and receiver. fundamental approach for uses a source-pathway-receiver model based one-way sonar equation, ...

Underwater acoustic networks have the potential to support a wide variety of applications from facilitating communication between autonomous underwater vehicles to supporting the remote monitoring of underwater mining equipment or environmental conditions [1]. Even though underwater acoustics has been studied for many years, and communications technologies exist for underwater scenarios, intere...

Underwater vocalisations of grey seals (Halichoerus grypus) were recorded by static acoustic monitoring (SM2M, Wildlife Acoustics) in the vicinity a colony located at White Strand beach on Great Blasket Island, southwest Ireland during pre-breeding and breeding seasons. Grey seal first classified across nine different categories based aural visual characteristics spectrograms, providing an repe...

Oki Electric was founded in 1881, as Japan’s first manufacturer of telecommunications equipment and devices. That year we succeeded in testing a prototype telephone and started on our way as “Oki, the acoustic technology company.” Since then, our history has spanned more than 120 years. From its start in acoustic technology, Oki Electric expanded into business activities related to marine indus...

Numerical solutions of the Helmholtz equation and the one-way Helmholtz equation are compared in the weak range dependence limit, where the overall range distance is increased while the range dependence is weakened. It is observed that the difference between the solutions of these two equations persists in this limit. The one-way Helmholtz equation involves a square root operator and it can be ...

We consider a model initial and boundary value problem for the wide-angle ‘parabolic’ equation Lur = icu of underwater acoustics, where L is a second-order differential operator in the depth variable z with depthand range-dependent coefficients. We discretize the problem by the Crank–Nicolson finite difference scheme and also by the forward Euler method using nonuniform partitions both in depth...

1 Abstract—Time Reversal (TR) is a technique to focus broadband signals tightly in time and space. Previously, this technique has been used in acoustics, medical and especially in underwater communication applications. It is capable of reducing noises, such as: Inter-Symbol Interference (ISI), InterUser Interference (IUI). . . , while the used equipments are more simple than complex Equalizers ...

This paper deals with the efficient numerical solution of the two–dimensional one– way Helmholtz equation posed on an unbounded domain. In this case one has to introduce artificial boundary conditions to confine the computational domain. The main topic of this work is the construction of so–called discrete transparent boundary conditions for state-of-the-art parabolic equations methods, namely ...