Abstract: In the present article it is shown that the presence of defects in a material for a certain duration of heat exposure leads to the necessity of taking into account the dependence of the linear thermal expansion coefficient on the mobility, which determines its operator form. Using the example of the dynamic thermoelastic problem with an inertial inclusion acting as the defect, the change in the thermoacoustic signal caused by its presence is demonstrated. The transfer function of this operator is obtained, the behavior of which corresponds to the experimental result.