This paper proposes using microphone recordings of air waves, recorded close to a geophone, to suppress air-wave noise on the geophone. The types of air-wave noise on the geophone may include air-coupled ground roll, air blast, ground-coupled air blast, and wind noise. Microphone recordings of air waves are related to ground measurements and geophone disturbances. We can thus attempt to use the...

An “acoustic vector sensor” (also known as a “vector hydrophone” in underwater or sea-surface applications) is composed of three orthogonally oriented uni-axial particle-velocity sensors, plus a “pressure-sensor” (i.e., a microphone or a hydrophone)—all collocated in a point-like spatial geometry. (This collocated setup is versatile for direction finding, because its azimuth-elevation spatial r...

Over the last three decades extensive research has been carried out towards the design and development of fibre optic hydrophones. The inherent advantages of fibre optic sensing technology, like high sensitivity, immunity to electromagnetic interference, intrinsic safety to water leakage, remote measurement capability etc. makes it an ideal choice for underwater acoustic sensing[1, 2]. The init...

The current primary method for hydrophone calibration is the three-transducer spherical-wave reciprocity at NPL, covering the frequency range between 1 kHz up to 500 kHz with expanded uncertainties as low as ± 0.5 dB. Optical methods can provide an alternative method for primary calibration as they directly measure the acoustic particle velocity at a specific point in the field. The hydrophone ...

Approximation of Green's functions through cross-correlation of acoustic signals in the ocean, a method referred to as ocean acoustic interferometry, is potentially useful for estimating parameters in the ocean environment. Travel times of the main propagation paths between hydrophone pairs were estimated from interferometry of ocean noise data that were collected on three L-shaped arrays off t...

This paper presents a geoacoustic inversion scheme relying on the inversion of signal close to marine mammals vocalizations on a single hydrophone in shallow waters. Our method makes best use of the multipath propagation of vocal calls and of their time-frequency signature to extract an observable used by the inversion algorithm to estimate sea bottom features. This method requires vocalization...

Fin whales are among the largest predators on earth, yet little is known about their foraging behavior at depth. These whales obtain their prey by lunge-feeding, an extraordinary biomechanical event where large amounts of water and prey are engulfed and filtered. This process entails a high energetic cost that effectively decreases dive duration and increases post-dive recovery time. To examine...

Although humpback whale (Megaptera novaeangliae) calves are reported to vocalize, this has not been measurably verified. During March 2006, an underwater video camera and two-element hydrophone array were used to record nonsong vocalizations from a mother-calf escort off Hawaii. Acoustic data were analyzed; measured time delays between hydrophones provided bearings to 21 distinct vocalizations ...

The common use of the bent-horn model of the sperm whale sound generator describes sperm whale clicks as the pulse series {p0, p1, p2, p3,...}. Clicks, however, deviate from this standard when recorded using off-axis hydrophones. The existence of additional pulses within the {p0, p1, p2, p3, ...} series can be explained still using the bent-horn model. Multiple reflections on the whale's fronta...

Some beaked whale species are susceptible to the detrimental effects of anthropogenic noise. Most studies have concentrated on the effects of military sonar, but other forms of acoustic disturbance (e.g. shipping noise) may disrupt behavior. An experiment involving the exposure of target whale groups to intense vessel-generated noise tested how these exposures influenced the foraging behavior o...