This study aimed to investigate the objective parameters of sound in relation to the types of materials on wall surfaces and the density of people attending the main prayer hall of the Car Mosque that was built in 19th century in the city of Trabzon (Turkey). The numerical values of objective parameters of sound in the prayer hall were simulated using Odeon version 10 computer software. The prayer hall was modelled for two different scenarios. In the first scenario, the materials on all surfaces of the prayer hall were assigned as in their current state. In the second scenario, wood was used as the simulation material on the surfaces of the side wall and rear wall facing qiblahh. In addition, the numerical values of the objective parameters of sound were estimated for three different scenarios: a full, semi-full and empty prayer hall. The results showed that the fullness of the prayer hall in the mosque and types of materials on surfaces could affect the objective parameter values of sound especially at low frequencies. The finding of this study would provide useful objective parameters of sound for different types of materials for construction of wall and ceiling surfaces of prayer halls in mosques.