We analyse the microstructure of an open nickel-chrome foam using computed tomography. The foam sample is modelled by a random Laguerre tessellation, i.e. a weighted Voronoi tessellation, which is fitted to the original structure by means of geometric characteristics estimated from the CT image. Using the Allard-Johnson model we simulate the acoustic absorption of the real foam and the model. Finally, simulations in models with a larger variation of the cell sizes yield first results for the dependence of acoustic properties on the geometric structure of open cell foams.