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Block III: Frequencies

A frequency loop has been incorporated in OAST to allow for computation of transmission loss over a wide frequency band in one run. The frequency specification (Block III in SAFARI Manual) has therefore been changed to:

FR1 FR2 NF COFF [V]

where FR1 and FR2 are the minimum and maximum frequencies, respectively. NF is the number of frequencies, spaced equidistantly between FR1 and FR2, except if option f was specified; then the frequencies will be spaced logarithmically. COFF is the complex wavenumber integration contour offset. To be specified in , where is the wavelength at the source depth SD. As only the horizontal part of the integration contour is considered, this parameter should not be chosen so large, that the amplitudes at the ends of the integration interval become significant. In lossless cases too small values will give sampling problems at the normal modes and other singularities. For intermediate values, the result is independent of the choice of COFF, but a good value to choose is one that gives 60 dB at the longest range considered in the FFT, i.e.


where the maximum FFT range is


This value is the default which is applied if COFF is specified to 0.0.

The optional parameter V is the identical speed of source and receiver relative to the medium, projected onto the radial vector connecting them. This parameter is only used for option d.


next up previous contents
Next: Block IV: Environmental Model Up: Input Files for OAST Previous: Block II: OAST options
henrik schmidt
1999-08-25