surface of sensor hfm_ 1 the low frequency signal components of air mass sensor signal l_ 1 which indicate the actual air mass flow form second auxiliary signal h_ 2 the cut off frequencies of filters 440 a 442 a are selected as a function of a model of internal combustion engine 1 and are dynamically adapted to the individual operating state with knowledge of the water quantity in intake tract 3 from first auxiliary signal h_ 1 the actual air mass from second auxiliary signal h_ 2 and from state variables of internal combustion engine 1 as well as possibly additional parameters of the combustion it is possible to calculate the air mass actually available in the combustion chambers of internal combustion engine 1 even with water in its liquid phase present in intake tract 3 of internal combustion engine 1 it is possible to operate internal combustion engine 1 at the optimal operating point another example embodiment of the present invention is shown in fig4 two hot film air mass sensors hfm_ 1 hfm_ 2 are arranged in intake manifold 4 at a clearance d with respect to one another the arrow indicates the flow direction of the air flowing into intake manifold 4 as can be gathered from fig4 first air mass sensor hfm_ 1 is first surrounded by an inflowing air volume and following a propagation delay as a function of clearance d second hot film air mass sensor hfm_ 2 is surrounded by the inflowing air volume as well first sensor hfm_ 1 provides air mass sensor signal l_ 1 and second sensor hfm_ 2 provides first auxiliary signal h_ 1 to compensate for the propagation delay difference between air mass sensor signal l_ 1 and first auxiliary signal h_ 1.