Practical modeling of acoustic losses in air due to heat conduction and viscosity

Accurate acoustics models of small devices with cavities and narrow slits and ducts should include the so‐called boundary layer attenuation caused by thermal conduction and viscosity. The purpose of this paper is to present and compare different methods for including these loss mechanisms in analytical and numerical models. A simple circular geometry with a narrow tube has been used as a reference and is investigated both through measurements and the different models. The simulation methods compared are: i) traditional analytical approaches such as lumped parameter modelling and transmission line modelling, ii) numerical methods implemented into commercial packages, such as the low reduced frequency models as proposed by W. M. Beltman and implemented in ACTRAN and the linearized Navier‐Stokes equations used in COMSOL Multiphysics, and iii) an implementation specifically made for this purpose using BEM and the full linearized model by M. Bruneau.