The vibrational characteristics of H atoms on Si surfaces were investigated by infrared spectroscopy while surface electric fields were controlled on several vicinal (111) surfaces. These surfaces were prepared in solution. By analyzing the response to the electric fields, the orientation of the dynamic polarizations, P(dyn)s, for specific vibration modes such as Si-H stretching and wagging were determined. These vibration modes are associated with specific bulk-terminated chemisorption sites for H atoms on such surfaces as the top layer of Si atoms of the (111) terrace, the [11 (1) over bar] micro facet of the [11 (2) over bar] step edge, and the [001] micro facet of the [<(11)over bar>2] step edge. The anisotropy of P(dyn)s also showed that these step edges were atomically straight along [(1) over bar 10] and had the translational symmetry of a Si crystal, meaning that these vibrations were not isolated but collective, and thus should be treated as parts of surface phonons. The deduced surface structures confirm previous infrared analyses. The scissoring vibration of dihydride at the [<(11)over bar>2] step edge, which had been missed previously, was also observed. It was found that the [<(11)over bar>2] step edge had a strained vertical dihydride and a strained monohydride complex. By adopting a three-layer model with an experimentally determined screening factor when analyzing P(dyn)s, we concluded that the dihydride was pulled up at an orientation angle of 21 degrees from its bulk-terminated position, in contrast with the other bulk-terminated structures. This is consistent with a Raman result [M. A. Hines et nl., J. Chem. Phys. 101, 8055 (1994)] and explains the discrepancy with the previous results of energy loss and infrared spectra regarding the step-edge structure.