[en] The kinetic energy included in the surface convection layers is roughly estimated for Cepheid variables. For homogeneous envelopes with the normal Population I composition, the total kinetic energy of convection in beat Cepheids is nearly equal to that in Cepheids without beat. This energy becomes larger for beat Cepheids than for normal Population I Cepheids, as the helium is enriched in their envelopes. The suggested helium enrichment in the outer envelopes of Cepheids may induce the spontaneously enhanced H sub(α) emission in beat Cepheids, while the emission is not found in normal Cepheids but redder ones. Distortions or emission of H sub(α) line in Cepheids could be an evidence to support the inhomogeneous envelope theory. (author)