Heavy fields coupled to the inflaton may give rise to transient reductions in the speed of sound of the adiabatic mode in the effective single-field theory. This effect translates into localized, correlated features in the primordial power spectrum and bispectrum. More importantly, there is a regime in which the correlation can be calculated analytically. This allows us to perform a statistical search for a feature in the power spectrum and predict the associated primordial bispectrum. We report on an ongoing search for such features in CMB and LSS data.