The work at hand focuses on an adaptive system aimed at improving the soundproof performance of car door seals at specific working regimes (cruise), without interfering with the conventional open-closure operations. The idea addresses the necessity of increasing the seal effectiveness, jeopardized by aerodynamic actions more and more important as the speed increase, generating a pressure difference between the internal and the external filed, in the direction of opening the door. To recover this effect, an expanding mechanism was integrated within the seal cavity, driven by an SMA actuator. The material was activated (heated) by Joule effect; its compactness, intrinsic of smart materials, contributed to arrive to a final system characterized by a high level of integrability (expanding cells). In this paper, the development process is described together with the verification activity, aimed at proving the functionality of the realized device. Starting from the industrial requirements, the most appropriate solution was identified highlighting the working principle and the main design parameters involved. Then, the envisaged system was designed and its executive digital mock up (CAD) was released. Prototyping and laboratory validation showed the reliability of the numerical models and the associated predictions. On this basis, the integration task within the actual reference car was faced. To demonstrate the isolation effect of the proposed system, an experimental campaign was finally organized in an anechoic room, achieving significant results on the concept value.