File:The-Sound-Generated-by-Mid-Ocean-Ridge-Black-Smoker-Hydrothermal-Vents-pone.0000133.g005.jpg

English: Contours of the spectra computed from the average spectral power of Puffer's acoustic signal in 5-Hz bands. The power level time-series have been normalized by their root-mean-square, thus the units of the contoured values are inverse cycles per day (cpd), and the relative magnitudes of the contours are only meaningful in the horizontal direction. The length of the time-series (136 hours) renders spectral information below ∼1 cycles per day unresolved. Semi-diurnal (∼1.95 cycles per day) variability of Puffer's acoustic power occurs within the ∼150–325 Hz and ∼450–500 Hz frequency bands.