Some of the embodiments of the present disclosure provide a method for analyzing a substance, where the method includes subjecting the substance to a dynamic excitation to produce an observable response, and determining a characteristic quantity of the substance based on a correlation between the excitation and the response. The correlation between the excitation and the response is expressed by a parametric model for which a specific model structure with a finite number of unspecified parameters is preset. The determining a characteristic quantity of the substance includes calculating the parameters of the model from values of the excitation and the response in a time domain, determining from the calculated parameters a transfer function in a frequency range, and calculating the characteristic quantity directly from the transfer function. Other embodiments are also described and claimed.