OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 6 4 Fig. 7. Converting the pulse sequence (а) into its spectrum (b, c, d): а – sf = 0.01; b – sf = 0.1; c – sf = 0.2; d – sf = 0.3 а b c d composition. In all cases there is a problem of estimating the noise immunity of the measured signal. Interferences caused by additional disturbances lie in the low-frequency region, and it can be reduced to variations of the shear area ΔS(t) [60]. The interference immunity of the signal can be estimated by the coherence function 2 2 , ( ) f X k ω between the power emission f(t) and the measured sequence. To calculate 2 2 , ( ) f X k ω it is convenient to move the perturbation point of ΔS(t) to the power, as shown by the dashed line in fig. 3. Then we have [ ] 2 1 2 , ( ) 1 ( ) k f X k - ω = + ∆ ω , (11) where 2 , 0 2 , ( ) ( ) ( ) 1 ( ) S S k f f S S T ∆ ∆ ω ρ ∆ ω = ω + ω ; , ( ) S S S∆ ∆ ω is a disturbance spectrum; , ( ) f f S ω is an emission spectrum. The analysis of 2 2 , ( ) f X k ω shows that as the frequency increases, the conditioning of the deformation displacements by the force emission increases. Example of vibroacoustic diagnostics. The above properties of frequency response can be used as a basis for the construction of information space. The compromise between complexity, noise immunity and informativeness, allows us to consider the following features. The first attribute takes into account the shift of the average frequency of the spectrum ωc, determined by the rule 0 ( ) ( ) Ñ Ñ S d S d ω ∞ ω ω ω = ω ω ∫ ∫ . The current value of ωc(t) is difficult to measure. It is easier to consider the following estimation: Ñ 1 1 0 0 0 0 Ï ( ) ( , ) ( ) ( ) Ñ w w S w d S d S d - ω ∞ ∞ ω = ω ω - ω ω ω ω ∫ ∫ ∫ , (12)
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