The prediction of vibration levels near underground trains is of growing importance for newly constructed infrastructures in cities. Before construction, preliminary studies of vibration impact need to be undertaken in order to identify the buildings that may be affected based on vibration contamination laws and modify the railway line or the type of superstructure if necessary. These studies need fast and economic models due to the large areas they need to cover. The present study aims at predicting the vibration impact for the new Line 9 of Barcelona Underground which is 48 km long. The solution presented is a fast pre-calculated 2D FEM model which is run once for a set of different soil types and tunnel depths, obtaining sets of surface vibration levels. Interpolating between the depths and distances of the tabulated results can be used as a very fast model for prediction. The model is calibrated with measurements in the same conditions (rolling stock and superstructure) as those expected in Line 9 and offers an accuracy not far from current 2.5D and 3D models.
Most cases of global active noise reduction in commuter turboprop aircraft cabins have been attempted at low frequencies. The case of noise reduction applications for a smaller piston engine aircraft has been studied less, although they are noisier than turboprops with levels of up to 100 dBA. Specifically, the case of a six-seat, two-engine aircraft is studied here for an active noise control application. The main frequencies for noise reduction have been found at BFP (75 Hz) and some harmonics, 225 and 375 Hz (according to A-weighted noise levels). Computer model analysis of the cabin shows that only the peak at 75 Hz could be globally controlled, so the local control strategy is selected for application. Zones of attenuation around the head of a hypothetical passenger and attenuation at their ear, applying local control strategy, are obtained for different configurations in laboratory and eventually tested under flight conditions.