Oceanic bubble population measurements using a buoy-deployed combination frequency technique

• Published in: IEEE journal of oceanic engineering Vol. 23; no. 4; pp. 400 - 410
• Main Authors: Phelps, A.D., Leighton, T.G.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-10-1998; Institute of Electrical and Electronics Engineers
• Subjects: Acoustic measurements; Acoustic scattering; Atmospheric measurements; Earth, ocean, space; Exact sciences and technology; External geophysics; Frequency measurement; Marine; Oscillators; Other topics; Physics of the oceans; Resonance; Resonant frequency; Sea measurements; Sea surface; Signal generators; Sea surface; Non linear oscillator; Instruments; Calibration; Measurement method; Air bubble; Underwater acoustics
• ISSN: 0364-9059; 1558-1691
• DOI: 10.1109/48.725234

This paper presents the results of using a combination frequency acoustic technique to measure the near-surface bubble population in the open sea. The combination frequency technique monitors the appearance of sum-and-difference signals generated by the nonlinear interaction of two sound fields: one, a high-frequency signal, scatters geometrically from the bubble, and the other, of much lower frequency, is used to excite the bubble into resonant pulsation. The text details the calibration of the apparatus necessary to relate the measured heights of the sum-and-difference terms to actual numbers of bubbles and describes the experimental procedure for the collection of the oceanic data. In total, six trials were performed over a one-day period, each comprising ten "snapshots" of the local bubble population at ten discrete radii. This data was augmented with simultaneous video, slide, and dictaphone records of the state of the sea around the measurement position.