Sound wave diffraction difference index for noise barrier with added device

The diffraction phenomenon at the edge of the acoustic screen is of fundamental importance for forming the acoustic shadow area in the space outside the screen. The so-called added devices construction solutions are increasingly used on plane sound barriers, often used as anti-noise solutions on roads and railway lines. Added devices with various geometric shapes; aim to change the diffraction conditions at the noise-reducing devices' top edge. Adrienne is a method developed in a European research project, the aim of which was the measurement on site of sound absorption and sound transmission of any road noise barrier. The European Adrienne project has developed a diffraction difference index at the top edge of an acoustic screen and a method for its determination to compare the effectiveness of the screen with and without the added device. The diffraction difference index is a single-number rating of the design solution mentioned. Measurements for index calculations are made by comparing the impulse response of screens with and without the added device using MLS (Maximum Length Sequence) signals.