The roar of Yasur: Handheld audio recorder monitoring of Vanuatu volcanic vent activity.
R. D. Lorenz, E. P. Turtle, R. Howell, J. Radebaugh, R. M. C. Lopes
Journal of Volcanology and Geothermal Resarch 322: 168-174, 15 August 2016
We describe how near-field audio recording using a pocket digital sound recorder can usefully document volcanic activity, demonstrating the approach at Yasur, Vanuatu in May 2014. Prominent emissions peak at 263 Hz, interpreted as an organ-pipe mode. High-pass filtering was found to usefully discriminate volcano vent noise from wind noise, and autocorrelation of the high pass acoustic power reveals a prominent peak in exhalation intervals of ~ 2.5, 4 and 8 s, with a number of larger explosive events at ~ 200 s intervals. We suggest that this compact and inexpensive audio instrumentation can usefully supplement other field monitoring such as seismic or infrasound. A simple estimate of acoustic power interpreted with a dipole jet noise model yielded vent velocities too low to be compatible with pyroclast emission, suggesting difficulties with this approach at audio frequencies (perhaps due to acoustic absorption by volcanic gases).