Theoretical and experimental study of excess noise in elastic solids

Experimental results of excessive mechanical noise detection for samples under small loads within the linear range of the dependence between the deformations and the mechanical strains are reported. Typical values of sample strains were (2–5)×107 N/m2. The mechanical noise investigation consisted in measuring the radial (“barrel-shaped”) oscillations of a cylinder compressed by screw press. Small displacement capacitive sensors with a resolution 10−11 cm (0.001 Å) in the frequency range 0.2–20 kHz were used. It has been found experimentally that for the sample made from an inhomogeneous material (limestone with marble impregnations) under loads that are far from being destructive (in the Hookʹs law region) the relationship between the mechanical noise power in the low-frequency region 5–12 kHz and mechanical strain is nonlinear, namely, quadratic, which is the first experimental confirmation of the existence of excessive mechanical noises in mechanical systems.