# calc_absorption

echopype.utils.uwa. calc_absorption frequency temperature=27 salinity=35 pressure=10 pH=8.1 sound_speed=None formula_source='AM'

Calculate sea water absorption in units [dB/m].

Parameters

- frequency: int or numpy array

  frequency [Hz]

- temperature: num

  temperature [deg C]

- salinity: num

  salinity [PSU, part per thousand]

- pressure: num

  pressure [dbars]

- pH: num

  pH of water

- formula_source: str, {“AM”, “FG”, “AZFP”}

  Source of formula used to calculate sound speed. “AM” (default) uses the formula from Ainslie and McColm (1998). “FG” uses the formula from Francois and Garrison (1982). “AZFP” uses the the formula supplied in the AZFP Matlab code. See Notes below for the references.

Returns

- Sea water absorption [dB/m].

Notes

Ainslie MA, McColm JG. (1998). A simplified formula for viscous and chemical absorption in sea water. The Journal of the Acoustical Society of America, 103(3), 1671–1672. https://doi.org/10.1121/1.421258

Francois RE, Garrison GR. (1982). Sound absorption based on ocean measurements. Part II: Boric acid contribution and equation for total absorption. The Journal of the Acoustical Society of America, 72(6), 1879–1890. https://doi.org/10.1121/1.388673

The accuracy of the simplified formula from Ainslie & McColm 1998 compared with the original complicated formula from Francois & Garrison 1982 was demonstrated between 100 Hz and 1 MHz.