R/attenuation.R

In maRce10/baRulho: Quantifying (Animal) Sound Degradation

#' Estimate attenuation of sound pressure level
#'
#' \code{attenuation} estimates atmospheric attenuation and atmospheric absorption.
#' @param frequency Numeric vector of length 1 with frequency (in Hertz).
#' @param dist0 Numeric vector of length 1 with distance (m) for the reference SPL.
#' @param dist Numeric vector of length 1 with distance (m) over which a sound propagates.
#' @param temp Numeric vector of length 1 with frequency (in Celsius). Default is 20.
#' @param rh Numeric vector of length 1 with relative humidity (in percentage). Default is 60.
#' @param pa Numeric vector of length 1 with atmospheric (barometric) pressure in Pa (standard: 101325, default). Used for atmospheric attenuation.
#' @param hab.att.coef Attenuation coefficient of the habitat (in dB/kHz/m).
#' @return Returns the geometric, atmospheric and habitat attenuation (in dB) as well as the combined attenuation.
#' @export
#' @name attenuation
#' @details Calculate the geometric, atmospheric and habitat attenuation and the overall expected attenuation (the sum of the other three) based on temperature, relative humidity, atmospheric pressure and sound frequency. Attenuation values are given in dB. The function is modified from http://www.sengpielaudio.com
## and https://scikit-maad.github.io/generated/maad.spl.attenuation_dB.html#maad.spl.attenuation_dB.
#' @examples {
#'   # measure attenuation
#'   attenuation(frequency = 2000, dist = 50, dist0 = 1)
#' }
#' @family miscellaneous
#' @author Marcelo Araya-Salas (\email{marcelo.araya@@ucr.ac.cr})
#' @references {
#' Araya-Salas, M. (2020). baRulho: baRulho: quantifying degradation of (animal) acoustic signals in R. R package version 1.0.2
#' }

attenuation <-
  function(frequency,
           dist0,
           dist,
           temp = 20,
           rh = 60,
           pa = 101325,
           hab.att.coef = 0.02) {
    # check arguments
    arguments <- as.list(base::match.call())
    
    # add objects to argument names
    for (i in names(arguments)[-1]) {
      arguments[[i]] <- get(i)
    }
    
    # check each arguments
    check_results <-
      .check_arguments(fun = arguments[[1]], args = arguments)
    
    # report errors
    .report_assertions(check_results)
    
    # atmospheric attenuation
    pr <- 101325 # reference ambient atmospheric pressure: 101.325 kPa
    To1 <- 273.16  # triple-point isotherm temp: 273.16 K
    To <- 293.15 #  reference temperature in K: 293.15 K (20°C)
    temp <- temp + 273.15 # celcius to farenheit
    
    #saturation vapor pressure equals
    psat <- pr * 10 ** (-6.8346 * (To1 / temp) ** 1.261 + 4.6151)
    
    # molar concentration of water vapor, as a percentage
    h <- rh * (psat / pa)
    
    # oxygen relaxation frequency
    fr0 <-
      (pa / pr) * (24 + 4.04e4 * h * ((0.02 + h) / (0.391 + h)))
    
    # nitrogen relaxation frequency
    frN <-
      (pa / pr) * sqrt(temp / To) * (9 + 280 * h * exp(-4.170 * ((temp / To) **
                                                                   (-1 / 3) - 1)))
    z <- 0.1068 * exp(-3352 / temp) / (frN + frequency ** 2 / frN)
    
    y <-
      (temp / To) ** (-5 / 2) * (0.01275 * exp(-2239.1 / temp) * 1 / (fr0 + frequency **
                                                                        2 / fr0) + z)
    
    atm_att_coef <-
      8.686 * frequency ** 2 * ((1.84e-11 * 1 / (pa / pr) * sqrt(temp / To)) + y)
    atm_att <- atm_att_coef * (dist - dist0)
    
    geom_att <- -20 * log10(dist0 / dist)
    
    hab_att <-
      hab.att.coef * frequency * (1 / 1000) * (dist - dist0)
    
    total_att <- geom_att + atm_att + hab_att
    
    outdf <-
      data.frame(
        frequency = frequency,
        dist = dist,
        geometric.attenuation = geom_att,
        atmopheric.attenuation = atm_att,
        habitat.attenuation = hab_att,
        combined.attenuation = total_att
      )
    
    return(outdf)
  }

##### modified from  http://www.sengpielaudio.com, http://www.sengpielaudio.com/calculator-air.htm
## and https://scikit-maad.github.io/generated/maad.spl.attenuation_dB.html#maad.spl.attenuation_dB