Wideband frequency subset
The operator suppresses the components of the data that lie outside the requested frequency range for a wideband acoustic variable.
The pulse length is not adjusted in the calculation for this operator, so when used with Sv data, it will result in lower Sv values.
Echoview accepts operands of the following data types as input:
Operand 1 |
|
Settings
The Wideband Frequency Subset Variable Properties dialog box pages include (common) Variable Properties pages and these operator pages:
Operands page
Wideband Frequency Subset page
Settings |
Description |
New start frequency (kHz) |
New start frequency in kHz. |
New end frequency (kHz) |
New end frequency in kHz. |
Notes:
- Start frequency must be less than end frequency.
- Default start frequency is 0kHz and default end frequency is 500kHz.
- The Wideband Frequency Subset operator will produce a result if the selected frequency range overlaps the frequency range of the input data.
- No data samples in the operand are handled as -999 dB for use in Fourier calculations. See also Wideband frequency response note.
- Operand samples with values of -999 dB or 9.9e+37 dB are handled as (0,0i) in Fourier calculations.
- Sv, TS and TVG calculations use the operand's center frequency and the resultant frequency dependent absorption coefficient.
- The frequency displayed in the echogram's title bar is the same as the input data, as the values used for the Sv and TS calculations remain the same all the way down the virtual variable chain.
- Frequency values can be specified using the LocalCal.
- Calculation precision when converting between dB and linear units
Algorithm
The band pass filter input is the data and center frequency from operand 1 and the New start frequency and New end frequency. The output data type is the data type for operand 1. The virtual variable retains the calibration of operand 1.