The acoustic to the parametric instability has been studied for H2-air mixtures at normal conditions. Two approaches for the investigation of the problem have been considered. The simplified analytical model proposed by Bychkov was selected initially. Its range of applicability resulted to be very restricted, and therefore, numerical solutions of the problem were taken into account. The results obtained were used to study the existence of spontaneous transition from the acoustic to the parametric instability for different fuel concentrations. Finally, the growth rate of the instabilities was numerically calculated for a set of typical mixtures for hydrogen safety