Radial temperature-gradient effects on transmission loss in dissipative silencers with elastic membrane wall segments

A two-dimensional axisymmetric hybrid finite element model is developed for dissipative silencers operating under radial thermal gradients and mean flow. The device couples a central airway to a fibrous absorbent annulus through either a perforated plate or a thin elastic membrane. The carrier-gas density and sound speed, lining flow resistivity, and equivalent-fluid properties vary with temperature, while the impedance interface enforces particle-velocity continuity. Acoustic pressure is discretised on a structured bilinear mesh; temperature-dependent properties are evaluated at Gauss points, and wall impedance is incorporated through coupling submatrices in one linear system, avoiding a separate cross-sectional eigenvalue or point-collocation step. The model is validated against a published high-temperature silencer benchmark. Increasing the inner-wall temperature from 200 to 400 ° C shifts the principal transmission-loss peak from 1540 to 1920 Hz and reduces its amplitude from 22.6 to 18.7 dB . The elastic membrane adds a tunable narrow-band attenuation peak governed by its hoop-stiffness resonance, whose frequency is insensitive to liner temperature. The results identify radial thermal gradients and membrane properties as largely independent design parameters for high-temperature duct noise control.