<p>This research investigates alternative methods for predicting sound transmission loss of duct liners and re-evaluates noise attenuation performance. A theoretical model based on mass-spring-damping parameters is used to analyze the transmission loss of Helmholtz resonators in ducts. The research compares analytical predictions with numerical simulations for both single and twin Helmholtz resonator configurations, examining the impact of resonator geometry, damping characteristics, and inter-resonator spacing. The ‘reactance-to-resistance’ effect is proposed to occur between resonators when placed in parallel. The results indicate that damping in a Helmholtz resonator can be used to achieve a balance between reflection and absorption effects. Resonator spacing influences system mass modification, revealing wavelength-related cyclic patterns. In addition, noncompact liner width and damping determine transmission loss performance across different frequency ranges. This research provides insights for improved duct liner design considering sound source effects and offers a deeper physical understanding of acoustic performance beyond traditional transmission loss metrics.</p>