High precision measurements of the velocityu, the attenuation α, and dispersionDof first sound have been made along the lambda line in4Hefor frequencies up to 1 MHz and for temperatures |T−Tλ| ⩽1 mK. Our data can be understood in terms of order‐parameter relaxation and order‐parameter fluctuations. We find that the time τ characterizing the relaxation process belowTλand the time τ characterizing the fluctuations both above and belowTλhave the same temperature and pressure dependence; that is, only one time scale is important very near the phase transition. The analysis of the attenuation due to fluctuations aboveTλallows us to determine a simple scaling law for all our data, valid over four decades in ωτ,α(T > Tλ)/α(T = Tλ) = ωτ/(c + ωτ), wherec≃ 0.5. A similar relation for the dispersion atT>Tλwas also determined.