The cryostat of gamma-ray spectrometer with HPGe detector cooled by Stirling cycle cryocooler is under consideration. The natural frequencies and modes shapes for components involved to oscillatory systems distinguished in dynamic model of cryostat were calculated by Solidworks simulation. The results obtained for the gamma-ray spectrometer “Monolith” produced by BSI, represent its specific modal portrait and allow identification the components of electrical noise due to microphone effect. The absence of resonant amplification due to coincidence between the harmonics of cryocooler operating frequency and the natural frequencies of the cryostat components is an important condition for reducing the influence of microphonics. The results obtained by modal analysis are also useful for assessing the influence of external mechanical disturbances, such as shocks, external vibration or audible noise.