The dependence of the position of a maximum and half-width of stretching bands of surface OH and OD groups of Aerosil perturbed by adsorbed pyridine is studied as a function of the amount of adsorbed molecules, sample temperature, and conditions of vacuum thermal processing. The observed shift of the absorption band maximum of perturbed OH groups upon variation of covering is explained by a change in relative intensities of the bands related to two types of adsorption, when a molecule forms a hydrogen bond with one or two OH groups. The 3450 cm^-1 band, which corresponds to the second hydrogen bond between the π-electron ring and the hydroxyl group, is observed as a shoulder of the band related to OH groups perturbed by the nitrogen atom of pyridine. The temperature dependence of the spectra is explained by anharmonic interaction with low-frequency vibrations of the complex.