Ultrasonics without a source: Thermal fluctuation correlations at mhz frequencies

Richard L. Weaver, Oleg I. Lobkis

Research output: Contribution to journalArticlepeer-review


Noise generated in an ultrasonic receiver circuit consisting of transducer and amplifier is usually ignored, or treated as a nuisance. Here it is argued that acoustic thermal fluctuations, with displacement amplitudes of 3 fm, contain substantial ultrasonic information. It is shown that the noise autocorrelation function is the waveform that would be obtained in a direct pulse/echo measurement. That thesis is demonstrated in experiments in which direct measurements are compared to correlation functions. The thermal nature of the elastodynamic noise that generates these correlations is confirmed by an absolute measurement of their strength, essentially a measurement of the sample temperature.

Original languageEnglish (US)
JournalPhysical review letters
Issue number13
StatePublished - 2001

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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