S4ECoB will develop and deliver a prototype to optimize the existent Building Management Systems (BMS) by means of acquiring, identifying, monitoring, and adding the parameter of "occupancy level" in buildings and surroundings to enhance operations and eliminate unnecessary consumptions of energy for Heating, Ventilation, Air Conditioning, Lighting (HVACL), and other existent production and consumption systems, maintaining users' comfort. This will be achieved through the integration of a low-cost novel network of audio sensors with other building sensing and controls and the improvement of the strategies and algorithms of automation and conditioning deployed, calibrated and validated in two shopping malls and one international airport in real operational situation in order to demonstrate that energy savings and benefits justify the investment, providing new market solutions and supporting reduction of climate change.