Two-dimensional visualisation of a travelling sound wave over porous medium

Prior research has demonstrated a variation in sound speed and a wave bending in the air when an acoustic wavefront approaches a porous medium at a grazing angle. The impact is found to be explicitly dependent on the frequency of the sound and the nature of the adjacent absorber. The current study expands the investigations by using a distributed array of eight microphones mounted on a single-axis motorised mover. The measurement setup allowed for an extensive collection of impulse responses within a confined area near a horizontally placed porous panel. The sensors captured a frequency sweep every 10 millimetres on multiple horizontal planes above the air-material boundary. Moreover, the array configuration allowed for simultaneous capture of wave propagation both above and outside the projection area of the absorbing material. The progression of a travelling wavefront is reconstructed as an image-sequence-based 2D animation on four discrete vertical planes, 60 cm by 50 cm each, traversing or passing outside the porous material.