Аннотация:To identify reliably the astrophysical neutrino events, a thorough calculation of the atmospheric neutrino background is required. In this work we calculate the atmospheric neutrino spectra in the energy range 100 GeV-10 PeV with usage of several hadronic models and a few parametrizations of the cosmic ray spectra, supported by experimental data, which take into account the knee. The neutrino flavor ratio, extracted from the IceCube data, possibly indicates that the conventional atmospheric electron neutrino flux obtained in the IceCube experiment contains an admixture of the astrophysical neutrinos in the range 20-50 TeV.