callsync: an R package for alignment and analysis of multi-microphone animal recordings

Abstract

SummaryTo better understand how vocalisations are used during interactions of multiple individuals, studies are increasingly deploying on-board devices with a microphone on each animal. The resulting recordings are challenging to analyse, since microphone clocks drift non-linearly and record the vocalisations of non-focal individuals as well as noise.Here we presentcallsync, an R package designed to align recordings, detect and assign vocalisations to the caller, trace the fundamental frequency, filter out noise and perform basic analysis on the resulting clips.We present a case study where the pipeline is used on a new dataset of six captive cockatiels (Nymphicus hollandicus) wearing backpack microphones. Recordings initially had drift of ∼2 minutes, but were aligned up to ∼2 seconds with our package. We detected and assigned 970 calls across two 3.5 hours recording sessions. We then used a function that traces the fundamental frequency and applied spectrographic cross correlation to show that calls coming from the same individual sound more similar.Thecallsyncpackage can be used to go from raw recordings to a clean dataset of features. The package is designed to be modular and allows users to replace functions as they wish. We also discuss the challenges that might be faced in each step and how the available literature can provide alternatives for each step.