Table 3 User-defined impulse noise removal parameters in Echoview®.
From: Sounding out life in the deep using acoustic data from ships of opportunity
Filter parameter | Unit | Description | Value used |
|---|---|---|---|
Exclusion threshold | dB re 1 m2 m−3 | The value of a time-varied threshold TVT(r) (dB re 1 m2 m−3) defined at 1 m range. This threshold will vary as a function of range from the transducer as: \(TVT(r)={S}_{v}\left(1\right)+20\,{{\rm{\log }}}_{10}r+2{\alpha }_{a}(r-1)\), where \({S}_{v}\left(1\right)\) (dB re 1 m2 m−3) is the volume backscattering strength at one-meter range r (m) and \({\alpha }_{a}\) (dB m–1) is the absorption coefficient. Any \({S}_{v}(r)\) values below this calculated \(TVT(r)\) were preserved from the impulse noise filter. | −170 |
Vertical size of smoothing window | Metre | Vertical window size used for smoothing. Corresponding horizontal smoothing window is one ping wide. | 5 |
Horizontal size of context window (\(W\)) | Number | Width of the context window (i.e. number of pings including the current ping) used to identify noise. | 3 |
Detection threshold (\(\delta \)) | dB re 1 m2 m−3 | The impulse noise removal threshold value. | 6 |
