Acrylic Fibers

Acrylic fibers form a compliant, high-loft porous layer that interacts directly with the incoming turbulent boundary layer.  As air passes through the fiber matrix, velocity gradients are redistributed, and small-scale eddies are broken down through viscous dissipation.  This reduces the amplitude of near-field pressure fluctuations (hydrodynamic pseudo-sound) convecting past the ear.  The result is a measurable attenuation of broadband wind noise, particularly in the low- to mid-frequency range where turbulent energy is most dominant.

​

Polyester Fibers 

Polyester fibers provide a more structurally stable porous medium that governs bulk flow resistance and permeability.  By partially allowing flow-through, the material modifies the local pressure field and weakens shear-layer development near the ear - functionally similar to a base-bleed effect.  This reduces large-scale coherent structures and stabilizes the wake region, leading to lower turbulence intensity and diminished pressure fluctuations.  The outcome is a smoother, more controlled flow field and reduced wind noise across a wide range of cycling speeds.

​

Simply Stated

Acrylic behaves like a soft, lossy turbulence absorber - very effective at damping wind noise, especially at lower speeds and larger eddy scales, and Polyester behaves like a flow-conditioning medium - it manages airflow rather than aggressively dissipating it.