The effect of an acoustic wave packet falling onto a thin 3D filament of vorticity is identified and analyzed. The wavelength of sound decreases to zero in a finite time in such a process. Therefore, even if viscosity is small the wave packets will reach the scales of strong viscous dissipation and get absorbed, transferring their energy to the thermal energy of the compressible vortex flow. The cross section of the sound absorption by multiple vortex filaments having an arbitrary 3D shape is derived. Applications to the theory of the second sound attenuation in He ii are discussed.