Green modular systems (GMS) are modular vertical systems made by panels containing a vegetated substratum hosting different plant species, which can be mounted on a opaque façade, as a cladding ventilated skin wall system. This technology is more and more widely adopted by designers. In literature there are some studies on the thermal behavior of these systems, but few quantitative data are available. Moreover significant and in-depth researches on the acoustic behavior of GMS are still not present. Within a research project a consistent analysis on the thermal performance of a GMS , with different substratum and three different plants (Lonicera, Bergenia and Heuchera), have been carried out and some acoustic measurements have been done. This work is focused on the experimental analysis concerning the acoustic behavior. In particular to evaluate the sound absorption coefficient of the GMS, the measurements were carried out in a reverberation chamber, on a surface of 12 m2 (according to EN ISO 354 Standard) on both the panel with vegetation and the panel with the bare substrate. The obtained spectra, in both cases, demonstrate that the GMS is highly performing, in terms of sound absorption.