Recent researches have proposed alternative formulas for the estimation of the vibration reduction index (Kij) at junctions. Among other aspects, the new approaches propose different expressions for the low, mid and high frequency ranges; the current recommendation in the Annex E of EN 12354 standard provides a single value for the whole frequency range. Vibration reduction index can also be evaluated for specific junctions (dimensions, characteristics) representative of those in a particular building. This work analyses the potential effect that the use of the new vibration reduction index expressions can have in the prediction of global sound insulation outputs at low frequencies for different French traditional concrete based buildings. Measured acoustic performance is compared to predicted performance obtained following the EN 12354 approach.