R/absorption.R

In tagtools: Work with Data from High-Resolution Biologging Tags

#' Calculates the absorption coefficient for sound in seawater
#'
#' @param freq frequency in Hz
#' @param temperature temperature in degrees C
#' @param d depth in meters
#' @return The sound absorption in dB per metre.
#' @note Input arguments can be scalars, or a mixture of vectors and scalars as long as each argument is either a vector of length nx1 (with n being the same for all vector arguments) or a scalar.
#' @note After Kinsler and Frey pp. 159-160
#' @export
#' @examples absorption(140e3, 13, 10)
absorption <- function(freq, temperature, d) {
  if (missing(d)) {
    stop("inputs for all arguments are required")
  }
  Ta <- temperature + 273
  Pa <- 1 + d / 10
  f1 <- 1.32e3 * Ta * exp(-1700 / Ta)
  f2 <- 1.55e7 * Ta * exp(-3052 / Ta)
  A <- 8.95e-8 * (1 + 2.3e-2 * temperature - 5.1e-4 * temperature^2)
  B <- 4.88e-7 * (1 + 1.3e-2 * temperature) * (1 - 0.9e-3 * Pa)
  C <- 4.76e-13 * (1 - 4.0e-2 * temperature + 5.9e-4 * temperature^2) * (1 - 3.8e-4 * Pa)
  absp <- A * f1 * freq^2 / (f1^2 + freq^2) + B * f2 * freq^2 / (f2^2 + freq^2) + C * freq^2
  return(absp)
}