Since natural ventilation is a sustainable approach to provide an appropriate environment in many applications with biological organisms, this technique is gaining more interest. A major drawback of natural ventilation is the inability to measure and control the actual ventilation rate through a building, which is crucial to control indoor air conditions, for energy use, and for monitoring of gaseous emissions.In this article, a new sensor concept is presented that has the potential to measure ventilation rates of naturally ventilated buildings. The sensor consists of 32 acoustical actuators that capture the overall velocity profile in a ventilated section or ventilation opening by using an integration algorithm. Typical nonuniform and low ventilation rates for natural ventilation were measured with an overall measurement error of 8% in the range from 200 to 1000 m3/h.Units: SI