High-resolution acoustic measurements in fluids and gases by a path length modulation technique

P. J. Hamot*, H. H. Hensley, W. P. Halperin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


An acoustic technique has been developed that permits high-resolution velocity measurements to be performed in liquids and gases under circumstances where the acoustic attenuation may become very large. This cavity resonance method has been demonstrated in cavities with lengths as small as 150 μm at acoustic frequencies up to 151 MHz. The acoustic path length is continuously adjusted by a piezoelectric bimorph controlled by feedback from a sensitive acoustic impedance spectrometer. The measurement of velocity then simply reduces to measurement of position of the bimorph, and this can be performed with high accuracy using a capacitance bridge. Absolute measurements of the attenuation of sound can also be performed with this arrangement. It is suggested that this approach will be useful for the study of collective excitations in quantum fluids.

Original languageEnglish (US)
Pages (from-to)429-448
Number of pages20
JournalJournal of Low Temperature Physics
Issue number5-6
StatePublished - Dec 1989

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Materials Science(all)
  • Condensed Matter Physics


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