Background noise analysis variables

The mean Sv (or corresponding NASC or ABC) due to a defined level of background noise can be calculated in Echoview and exported in terms of the three analysis variables Sv_noise, NASC_noise and ABC_noise. The background noise variables can be used to correct integration variables for background noise by subtraction, but this correction must be done outside of Echoview.

The following parameters are needed for calculating the background noise:

On the Calibration page of the Variable Properties dialog box:

AbsorptionCoefficient

  • absorption coefficient (dB/m)

TvgRangeCorrection

  • This is the time-varied gain range correction equation specified for your data. Some data formats may have a default TvgRangeCorrection equation. When no TvgRangeCorrection is available the range of the sample is used.

On the Analysis page of the Variable Properties dialog box:

BN0 - background noise Sv at 1 m from the transducer face (dB re 1 m-1)

The background noise function BN in terms of r, the range from the transducer is:

BN(r) = BN0 + 20 log (r) + 2α (r-1)

where:

r = range or corrected range from the transducer face (m)

α = absorption coefficient (dB/m)

The background noise for a region, cell or selection is calculated as follows:

See also

ABC and NASC
Background noise in Echoview

Logged draft warning

Simrad Time Varied Gain Range correction
About time varied gain