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.
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.