title: Improvements to the methods used to measure bubble attenuation using an underwater acoustical resonator.
abstract: Active acoustic techniques are commonly used to measure oceanic bubble size distributions, by inverting the bulk acoustical properties of the water (usually the attenuation) to infer the bubble population. Acoustical resonators have previously been used to determine attenuation over a wide range of frequencies (10-200 kHz) in a single measurement, corresponding to the simultaneous measurement of a wide range of bubble sizes (20-300 μm radii). However, there is now also considerable interest in acquiring measurements of bubbles with radii smaller than 16 μm, since these are thought to be important for ocean optics and as tracers for near-surface flow. To extend the bubble population measurement to smaller radii, it is necessary to extend the attenuation measurements to higher frequencies. Although the principles of resonator operation do not change as the frequency increases, the assumptions previously made during the spectral analysis may no longer be valid. In order to improve the methods used to calculate attenuation from acoustical resonator outputs, a more complete analysis of the resonator operation is presented here than has been published previously. This approach allows for robust attenuation measurements over a much wider frequency range and enables accurate measurements from lower-quality spectral peaks.
authors.affiliation: Graduate School of Oceanography, University of Rhode Island, South Ferry Road, Narragansett, Rhode Island 02882, USA. H.Czerski.97@cantab.net
authors.forename: Helen
authors.initials: H
authors.lastname: Czerski
authors.forename: Svein
authors.initials: S
authors.lastname: Vagle
authors.forename: David M
authors.initials: DM
authors.lastname: Farmer
authors.forename: Nick
authors.initials: N
authors.lastname: Hall-Patch
mesh_terms: D000162:Acoustics / Q000295:instrumentation*; D004867:Equipment Design; D005740:Gases; D008962:Models, Theoretical; D009038:Motion; D009792:Oceans and Seas; D010316:Particle Size; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013018:Sound Spectrography; D013997:Time Factors; D014159:Transducers; D014867:Water
chemical_list: D005740:Gases; D014867:Water