findEchoTimes: Find Estimated Echo Times
In PAMmisc: Miscellaneous Functions for Passive Acoustic Analysis

findEchoTimes

R Documentation

Find Estimated Echo Times

Description

Finds the estimated times of echoes in a waveform clip. This function was developed to estimate the time of a surface reflected echo of echolocation clicks of deep diving marine mammals. The times of echoes are estimated by finding peaks in the autocorrelation of a signal.

Usage

findEchoTimes(
  wav,
  sr = NULL,
  filter = NULL,
  clipLen = 0.03,
  peakMin = 0.01,
  minTime = 0.001,
  maxTime = NULL,
  channel = NULL,
  n = 3,
  plot = TRUE,
  plotText = NULL
)

Arguments

`wav`	waveform to find echoes in. Can be a numeric vector, Wave, or WaveMC class object
`sr`	sample rate of the waveform, if `wav` is a `Wave` or `WaveMC` object it will use the `samp.rate` slot
`filter`	filter to apply to `wav`, a vector of two numbers specifying the lower and upper bounds of the filter in Hz. A first value of `0` means no highpass filter is applied, a second value greater than `sr/2` means no lowpass filter is applied.
`clipLen`	length of clip (seconds) to analyse for echoes, measured from start of `wav`
`peakMin`	minimum magnitude of autocorrelation value to be considered a possible peak
`minTime`	minimum allowed echo time (seconds), this should be large enough to avoid correlating the original pulse with itself
`maxTime`	maximum allowed echo time (seconds)
`channel`	if `wav` has multiple channels, channel to use
`n`	the number of potential echoes to return, times with the `n` highest autocorrelation magnitude will be returned
`plot`	logical flag to create plot, will create a two-panel plot of the waveform (top) and the autocorrelation (bottom). Points of the selected candidate echo times are also drawn
`plotText`	optional text to plot on the upper waveform plot