Randall Balestriero

Enhanced feature extraction using the Morlet transform on 1 MHz recordings reveals the complex nature of Amazon River dolphin (Inia geoffrensis) clicks

The Amazon River dolphin lives exclusively in freshwater throughout the Amazon River watershed, a dynamic and acoustically complex habitat. Although generally considered a relatively non-vocal species, recent evidence suggests that these animals are acoustically active, producing tremendous quantities of high-frequency, pulsed signals. Moreover, these pulsed signals appear to be considerably more complex than previously believed. This study explored the high-frequency pulsed emanations produced by Amazon River dolphins in Peru. Audio recordings were made using a two hydrophone array, one of which was sampled at 1 MHz, in August of 2015. Digitized recordings were analyzed using FFT and Morlet wavelets. Subsequently, unsupervised machine learning attempted to delineate various click categories based upon inter-click intervals, the frequency bandwidth of each click, and the formants contained within each click. Although the Morlet transform is much more robust and accurate for higher frequencies than the FFT...

Heterogeneity of Amazon River dolphin high-frequency clicks: Current Odontoceti bioacoustic terminology in need of standardization

The quality and quantity of acoustical data available to researchers are rapidly increasing with advances in technology. Recording cetaceans with a 500 kHz sampling rate provides a more complete signal representation than traditional sampling at 96 kHz and lower. Such sampling provides a profusion of data concerning various parameters, such as click duration, inter-click intervals, frequency, amplitude and phase. However, there is disagreement in the literature in the use and definitions of these acoustic terms and parameters. In this study, Amazon River dolphins (Inia geoffrensis) were recorded using a 500 kHz sampling rate in the Peruvian Amazon River watershed. Subsequent spectral analyses, including time waveforms, fast Fourier transforms and wavelet scalograms, demonstrate acoustic signals with differing characteristics. These high-frequency, broadband signals are compared, and differences are highlighted, despite the fact that currently an unambiguous way to describe these acoustic signals is lackin...

All clicks are not created equally: Variations in high-frequency acoustic signal parameters of the Amazon river dolphin (Inia geoffrensis)

The quality and quantity of acoustical data available to researchers are rapidly increasing with advances in technology. Recording cetaceans with a 500 kHz sampling rate provides a more complete signal representation than traditional sampling at 96 kHz and lower. Such sampling provides a profusion of data concerning various parameters, such as click duration, inter-click intervals, frequency, amplitude, and phase. However, there is disagreement in the literature in the use and definitions of these acoustic terms and parameters. In this study, Amazon River dolphins (Inia geoffrensis) were recorded using a 500 kHz sampling rate in the Peruvian Amazon River watershed. Subsequent spectral analyses, including time waveforms, fast Fourier transforms and wavelet scalograms, demonstrate acoustic signals with differing characteristics. These high frequency, broadband signals are compared, and differences are highlighted, despite the fact that currently an unambiguous way to describe these acoustic signals is lacki...