Brief description
This dataset contains audio files, acoustic indices and false colour spectrograms for TERN Alice Mulga SuperSite. Acoustic recorders were set up to record for a total of 12 hours per day, split between six hours around dawn and six hours around dusk. The recording schedule aimed at capturing morning and evening bird choruses while minimizing memory and battery requirements.
Acoustic indices and false colour spectrograms were created for the recordings. Acoustic indices are summaries of the distribution of the acoustic energy in a recording. They are particularly useful for the analysis of long-term recordings of the environment and can be used to identify sound sources of interest, characterise the soundscape, aid in the assessment of fauna biodiversity, monitor temporal trends and track environmental changes. False colour spectrograms are visual representation of individual acoustic indices or combination of multiple indices. They can highlight the presence of specific sound sources, e.g. birds, insects or weather events, providing a tool for navigating long-term recordings.
The Alice Mulga SuperSite was established in 2010 at Pine Hill Cattle Station with research plots located in low open woodland Mulga (Acacia aneura) and non-Acacia, hummock grassland, and river red gum forest. The core 1 ha plot is located in a dense Mulga woodland (cover 70–80%). For additional site information, see https://www.tern.org.au/tern-observatory/tern-ecosystem-processes/alice-mulga-supersite/ .
An acoustic recorder was deployed at this site in the centre of the core 1 ha plot.
Notes
Data ProcessingAcoustic indices and false colour spectrograms were created using the software AnalysisPrograms (version 19.2.2.1)
Lineage
Acoustic indices are calculated using the software AnalysisProgram version 19.2.2.1. Long term recordings are resampled at 22.05 kHz and divided into one minute long segments. Acoustic indices are calculated for each segment.
Spectral indices are calculated on one minute long spectrograms. Each spectrogram is created by first dividing the one minute long recording into frames of 512 samples each and then calculating the Fast Fourier Transform for each frame. The frequency resolution is 43.1 Hz. The spectra are smoothed using a moving average window of width three and spectral amplitude values are converted into spectral power or decibels (dB).
Summary indices are calculated on the waveform envelope or are derived from the spectrograms. The wave envelope is created by taking the maximum absolute value in each frame. Absolute values are converted to dB.
False colour spectrograms are produced for each spectral index and combination of indices.
dB values are in reference to a hypothetical signal of unit amplitude.
Before the indices are calculated, noise is removed form both the waveform and the spectrogram using a modified versions of Lamel's adaptive level equalization (Lamel et al., 1981).
Entropy values are subtracted from 1 to obtain a measure of energy concentration; this provides a more intuitive index.
To create false colour spectrograms indices are normalised between a minimum and maximum value. These values affect only the visualization and are provided in the configuration file under the data access link.
DIFsp and SUMsp are used only for internal checks.
Notes
CreditWe at TERN acknowledge the Traditional Owners and Custodians throughout Australia, New Zealand and all nations. We honour their profound connections to land, water, biodiversity and culture and pay our respects to their Elders past, present and emerging.
The Alice Mulga SuperSite was established in 2010 in partnership with the University of Technology Sydney. The Alice Mulga SuperSite infrastructure was transferred in 2021 to James Cook University Cairns.
This work was funded by the Terrestrial Ecosystem Research Network (TERN), an Australian Government National Collaborative Research Infrastructure Strategy (NCRIS) project.
Long-term acoustic recordings are collected to characterise the acoustic sources in the ecosystem. Recordings can be used to estimate biodiversity, monitor temporal changes in the soundscape, compare the acoustic characteristics of different locations, and assess the effect of particular events such as bushfires and floods.
Created: 2012-10-17
Issued: 2022-01-21
Modified: 2014-07-14
Data time period: 2012-10-17
text: Located at Pine Hill Cattle Station, north of Alice Springs in the Northern Territory.
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Point-of-truth metadata URL- global : 53c8734c-0dcb-45b5-a027-3a9d1af24dbe
- URI : https://geonetwork.tern.org.au/geonetwork/srv/eng/catalog.search#/metadata/53c8734c-0dcb-45b5-a027-3a9d1af24dbe
