Effects of different sound insulation mortar materials in the wall system on human perceived airborne sound insulation performance in different frequency bands

Sound insulation mortars can enhance the airborne sound insulation (ASI) performance of walls, but the effect of these mortars on human acoustic perception remains under-researched. This study investigated the effects of three mortar types (lightweight sound insulation mortar (LSIM), ordinary mortar (OM), heavyweight sound insulation mortar (HSIM)) and three thicknesses (20, 30, 40 mm) of mortar layer of walls on human annoyance. Finite element analysis was first performed to obtain the sound transmission loss (STL) of the investigated walls. Five sound signals (neighboring music and speech, construction noise, and two traffic noises) were recorded and filtered using the STL of different walls to simulate sound transmission through the walls. A two-stage psychoacoustic experiment (Two-alternative choice and Likert-scale rating) using filtered sound stimuli was conducted with 68 participants, and VR was used to recreate the visual environment of a residential living room. The results showed that, under all noise types, the HSIM walls provided significantly superior perceived ASI performance than OM walls, while LSIM walls performed the poorest, especially under low-frequency dominant noise (construction and traffic noise). GLMM results further confirmed that perceived ASI performance was dominated by low-frequency STL components (125–500 Hz, p < 0.001). Increasing mortar thickness reduced annoyance but exhibited a clear diminishing marginal effect, with optimal thicknesses of approximately 44 mm for traffic noise and 31 mm for speech noise. This study provides a perception-based approach to enhance the perceived ASI performance of walls using sound insulation mortar in design and renovation.