Abstract: The sound absorption properties of cone and linear transition pine wedges were investigated in a pulse tube. It was found that: 1) the cut-off wave length of cone wedges is about 40 to 60% of the wedge length, 2) the ratio of the wedge length to the whole length has an optimum value for pine wedges, in order to give a minimum value of reflexion factor, 3) 20 cm pine wedges can be used as absorbers in anechonic tanks with a cut-off frequency around 10 KHz. The complex sound velocity of pine was represented also.