The equivalent beam angle is computed numericaily, according to its rigorous definition, for each of two transducers. These are those used with the SIMRAD split-beam echo sounders at 38 and 70 kHz. The results are expressed ...

The farfield beam pattern of each of two different split-beam transducers is computed and represented in the axial region by a finite number of constant levels. The accuracy of representation is determined as a function ...

The entrance region to Tysfjorden was acoustically surveyed a total of eleven times during the December 1996 abundance survey of the spawning stock of Norwegian spring-spawning herring (Clupea harengus). The observations ...

The influence of the swimming movement on fish target strength is investigated through a modelling exercise. In this, several gadoid specimens are represented as acoustic scatterers through their triangulated swimbladder ...

Nominal values for the equivalent beam angle are given for several transducers. These are the standard split-beam transducers designed for the SIMRAD EK500 scientific echo sounder, with operating frequencies of 38 and 120 ...

Acoustic abundance estimation of dense, vertically extended aggregations of fish requires knowledge of the extinction cross section. An established method based on a comparison of the area backscattering coefficients ...

There have been many experimental studies on acoustic shadowing, but once the effect is quantified, how is the compensation to be effected? This work shows how, through postprocessing of stored time series, containing ...

In-situ target strengths of six fishes were determined with a split-beam echo sounder during cruises about Lofoten in March 1984 and the Shetland Islands in July 1984. The species and lengths, mean and standard deviation, ...

The hibernating stock of Norwegian spring-spawning herring has been acoustically surveyed in a fjord system in northern Norway in December 1992. The survey frequencies are 18, 38, 120, and 200 kHz. When the corresponding ...