A nondimensional number(Δp/ρ)12/ftforprimary Pfeifentönerelating the dependence of differential pressure Δpacross orifice to density of gas ρ, thicknesstof orifice‐plate terminating pipe, and frequencyfofprimary Pfeifentöneis obtained by dimensional analysis. Correlation of experimental data presented on the basis of this number indicates that it is relatively constant in numerical value over range of variation of the parameters, pipe length, orifice diameter, differential pressure across orifice, andPfeifentonfrequency, studied.