This article synthetically presents the possibilities of application of the ENF criterion during testing the authenticity of the audio recordings aimed to determine the date of their registration. The authors conducted a series of experiments to try to determine the parameters, which should be analysed in the recording so as to ensure the reliability and reproducibility of the test results. Anonymised analysis of subject materials from actual cases were provided for testing. The obtained results allow to conclude that the accuracy of the designation of the date of registration depends primarily on the duration of the recording. High value of obtained correlation does not prove the correctness of the designated date and time. The shorter the duration of the mains hum signal extracted from the recorded evidence, the greater the probability of fitting a random segment of the course of the power grid electricity frequency. The value of the SNR is irrelevant as long as the applied detection algorithm of the hum, in any given moment of time, effectively sets the value of the frequency of the hum.