David L. Bradley

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The increase of ocean noise documented in the North Pacific has sparked concern on whether the observed increases are a global or regional phenomenon. This work provides evidence of low frequency sound increases in the Indian Ocean. A decade (2002-2012) of recordings made off the island of Diego Garcia, UK in the Indian Ocean was parsed into time series(More)
From 1998 to 2001, 115 h of acoustic recordings were made in the presence of the well-studied St. Lawrence population of blue whales, using a calibrated omnidirectional hydrophone [flat (+/- 3 dB) response from 5 to 800 Hz] suspended at 50 m depth from a surface isolation buoy. The primary field site for this study was the estuary region of the St. Lawrence(More)
The relationship between the bandwidth of a signal and the correlation of that signal with its ocean surface reflected arrival, a quantity we term frequency correlation, has been investigated experimentally and compared with two theories. Decorrelation of wideband surface scattered signals is a direct consequence of time spread. The acoustic measurement(More)
Northern resident killer whale pods (Orcinus orca) have distinctive stereotyped pulsed call repertoires that can be used to distinguish groups acoustically. Repertoires are generally stable, with the same call types comprising the repertoire of a given pod over a period of years to decades. Previous studies have shown that some discrete pulsed calls can be(More)
Frequency dependent measurements of attenuation and/or sound speed through clouds of gas bubbles in liquids are often inverted to find the bubble size distribution and the void fraction of gas. The inversions are often done using an effective medium theory as a forward model under the assumption that the bubble positions are Poisson distributed (i.e.,(More)
Intensity fluctuations were measured during August 2002 near San Diego using 20 and 40 kHz cw and fm signals. Source-receiver separation was 1km; source depths were 10m to 67m; receiver hydrophone depths were 44m to 217m. A 15-element chain of CTD sensors was towed to measure horizontal temperature and salinity with 1m resolution. Comparing the spectra of(More)