Contour plot of the transfer mobility (magnitude) in decibels normalized to the highest value on the surface. The response positions for the accelerometer are on the Perspex plate with five different excitation positions for the force hammer (indicated by the red * symbol) on the Aluminium plate. Results are shown at the following narrow band frequencies: (a) 125 Hz, (b) 500 Hz, (c) 1k Hz and (d) 5k Hz.