The relationship between air permeability and fabric characteristics such as fabric weight, thickness and density in a variety of nonwoven types has already been investigated. The effect of porosity on air permeability has also been thoroughly evaluated in numerous research works. However in this paper we report the effects of the specific energy in hydroentanglement on the air permeability of the resultant fabric. It is shown that within the ranges of the measurements, energy is not the only factor that affects the permeability. Although the same web weight is used in all trials, fabric weights and thicknesses did not show any clear or linear decrease when the energy given to the fabric was increased. The alteration of web weights and thicknesses under enhanced energy shows that entanglement mechanism in these nonwovens is not not as simple as we had expected. It is thought that the flow corridors in nonwovens are certainly very complex. This increased intricacy may be due to the randomness of nonwoven structures or the method of bonding such as the random hydroentanglement of spun-laced fabrics.