US Patent 10456536 Inhaler with two microphones for detection of inhalation flow

An inhaler with a housing (H) comprising an air-inlet (A_I) and a an air-outlet (A_O). Inside the housing (H) a flow path (FP) is defined between air-inlet (A_I) and air-outlet (A_O) where a dispenser (DP) is arranged to dispense an aerosol or a dry powder in the flow path (FP). Two sensors (S1, S2), e.g. microphones, are positioned spaced apart at external surfaces of the housing (H) to sense sound or vibrations resulting from a flow in the flow path (FP) at two different positions. This allows a precise detection of flow velocity during inhalation based on the sound or vibrations sensed by the two sensors (S1, S2), thus allowing examination of correct use of the inhaler. Further, the use of two spaced apart sensors (S1, S2) facilitates identification of priming and firing events in the sensed sound or vibrations which may also be used in evaluating the use of the inhaler. Preferably, a noise reduction algorithm is used that exploits the differences in the captured sound or vibrations from the two sensors (S1, S2), so at to allow precise flow measurements even in noisy environments.