Friday, 20 August 2010

Asian Elephant Vocalizations

Periodically at work we get e-mails telling us of new corpora that we can order as a member of the LDC. Usually these aren't particularly interesting e-mails but a few days ago there was an announcement of a new corpus of (yes you guessed it) Asian Elephant Vocalizations. I leave you with the official announcement of this fascinating corpus!

[This corpus] consists of 57.5 hours of audio recordings of vocalizations by Asian Elephants (/Elephas maximus/) in the Uda Walawe National Park, Sri Lanka, of which 31.25 hours have been annotated. The collection and annotation of the recordings was conducted and overseen by Shermin de Silva, of the University of Pennsylvania Department of Biology; voice recording field notes are of Shermin de Silva and Ashoka Ranjeewa. The recordings primarily feature adult female and juvenile elephants. Existing knowledge of acoustic communication in elephants is based primarily on African species (/Loxodonta africana/ and /Loxodonta cyclotis/). There has been comparatively less study of communication in Asian elephants.

This corpus is intended to enable researchers in acoustic communication to evaluate acoustic features and repertoire diversity of the recorded population. Of particular interest is whether there may be regional dialects that differ among Asian elephant populations in the wild and in captivity. A second interest is in whether structural commonalities exist between this and other species that shed light on underlying social and ecological factors shaping communication systems.

Data were collected from May, 2006 to December, 2007. Observations were performed by vehicle during park hours from 0600 to 1830 h. Most recordings of vocalizations were made using an Earthworks QTC50 microphone shock-mounted inside a Rycote Zeppelin windshield, via a Fostex FR-2 field recorder (24-bit sample size, sampling rate 48 kHz). Recordings were initiated at the start of a call with a 10-s pre-record buffer so that the entire call was captured and loss of rare vocalizations minimized. This was made possible with the 'pre-record' feature of the Fostex, which records continuously, but only saves the file with a 10-second lead once the 'record' button is depressed.

Certain audio files were manually annotated, to the extent possible, with call type, caller id, and miscellaneous notes. For call type annotation, there are three main categories of vocalizations: those that show clear fundamental frequencies (periodic), those that do not (a-periodic), and those that show periodic and a-periodic regions as at least two distinct segments. Calls were identified as belonging to one of 14 categories. Annotations were made using the Praat TextGrid Editor , which allows spectral analysis and annotation of audio files with overlapping events. Annotations were based on written and audio-recorded field notes, and in some cases video recordings. Miscellaneous notes are free-form, and include such information as distance from source, caller identity certainty, and accompanying behavior.

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