R/sweptsine.R

In sonicscrewdriver: Bioacoustic Analysis and Publication Tools

#' Generate a sine sweep
#'
#' Generates a frequency swept sine wave (either linear or logarithmic) and
#' returns it as a Wave object or vector.
#'
#' @param f0 Start frequency
#' @param f1 End frequency
#' @param mode One of "linear", "log"
#' @param sweep.time Duration of swept wave
#' @param time.unit One of "seconds", "samples"
#' @param samp.rate Sample rate of swept wave
#' @param output "wave" for a Wave object, or "vector"
#' @param ... Additional arguments to pass to data2Wave
#' @export
#' @return A swept wave object of the type specified in output.
#' @examples
#' #Generate a swept sine wave between 0Hz and 10kHz.
#' w <- sweptsine(0, 10e3)
#'
#' #Generate a swept sine wave between 0Hz and 10kHz and normalise it.
#' w <- normalise(sweptsine(0, 10e3))
#'
#' #Generate a stereo swept sine wave between 100Hz and 1KHz.
#' w <- tuneR::stereo(sweptsine(100, 1e3))
#'
#' #Generate an exponentially swept sine wave between 100Hz and 1KHz.
#' w <- sweptsine(100, 1e3, mode="log")
#'
sweptsine <- function(f0=100, f1=2500, mode="linear", sweep.time=1, time.unit="seconds", samp.rate=44100, output="wave", ...) {
  if (!output %in% c("wave", "vector")) {
    stop("output must be one of 'wave' or 'vector'")
  }
  if (f1 <= f0) {
    stop("sweptsine: f1 must be greater than f0")
  }
  if (time.unit == "seconds") {
    vector_length <- samp.rate*sweep.time
  } else if (time.unit == "samples") {
    vector_length <- sweep.time
  } else {
    stop("time.unit must be one of 'seconds' or 'samples'")
  }

  if (mode == "linear") {
    w <- sweptsine.lin(f0, f1, sweep.time, samp.rate, vector_length)
  } else if (mode == "log") {
    w <- sweptsine.log(f0, f1, sweep.time, samp.rate, vector_length)
  } else {
    stop("mode must be one of 'linear' or 'log'")
  }

  if (output == "vector") {
    return(w)
  }
  if (output == "wave") {
    return(data2Wave(w, samp.rate=samp.rate, remove.offset=FALSE, ...))
  }
}

sweptsine.lin <- function(f0, f1, sweep.time, samp.rate, vector_length) {
  delta_f <- (f1 - f0) / vector_length
  f <- seq(from=f0, by=delta_f, length=vector_length)
  phi <- seq(from=0, by=pi*f/samp.rate, length=vector_length)
  x <- sin(phi)
  return(x)
}

sweptsine.log <- function(f0, f1, sweep.time, samp.rate, vector_length) {
  delta_t <- sweep.time / vector_length
  t <- seq(from=0, by=delta_t, length=vector_length)
  R <- log(f1/f0)
  x <- sin((2*pi*f0*sweep.time/R)*(exp(R*t/sweep.time)-1))
  return(x)
}