Measurement of sound field in cavitating media by an optical fibre-tip hydrophone.
A fibre-optic technique was applied to measure the sound field in an ultrasonic cleaning vessel under practical conditions. A metal-coated fibre-tip is used as a sensor and a heterodyne interferometer detects the change in the optical path resulting from the movement of the fibre-tip in the sound field. Spectrally resolved sound field parameters such as the fundamental, the subharmonic or cavitation noise are extracted from the measurements and compared with results obtained by a piezo-electric hydrophone. It was found that the fibre sensor provides a signal related to the velocity in the sound field, but the information about cavitation-related parameters is similar to the information for pressure sensing techniques. The fibre-optic sensors have a uniquely high spatial resolution and the sound detection process is strongly influenced by single cavitation events close to the small fibre-tip. This paper shows that fibre-tip sensors are an alternative to common hydrophone techniques. They can open up new possibilities for measurement problems for which so far no solution exists, in particular when a high spatial resolution is required or when the measurement site is small.
Koch
Christian
C
Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany. Electronic address: ultrasonics@ptb.de.
Jenderka
Klaus-Vitold
KV
Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
D000465:Algorithms; D004563:Electrochemistry; D005336:Fiber Optic Technology; D007202:Indicators and Reagents; D008670:Metals; D014025:Titanium / Q000737:chemistry; D014465:Ultrasonics
D007202:Indicators and Reagents; D008670:Metals; D014025:Titanium