Historical structure properties and indoor requirements should be taken into consideration in plaster layer mixture type selection during the historical building restoration. In the research, it has been aimed to increase the sound absorption coefficient in plaster layers with the direction of accurate restoration application decisions. In the plaster content, natural hydraulic lime binder which is frequently used in historical building restoration was researched and the pumice aggregate type instead of river sand aggregate was investigated to show the effect of lightweight aggregate type. The experimental analyses which are sound absorption, compressive strength, flexural strength, capillarity of water absorption and open porosity, were performed to compare different plaster layer types. The effects of aggregate combination volumetric ratio, polypropylene fiber ratio, flax fiber ratio, and crumb rubber additive ratio were analyzed. It was understood that sound absorption coefficients can be enhanced by means of the mortar mixture content changes and the use of lightweight aggregate type. Especially, the use of pumice aggregate instead of river sand aggregate in the mortar mixture can significantly increase the sound absorption coefficient in the range of 1400-2700 Hz. Also, the use of pumice aggregate instead of river sand aggregate has increased compressive strength and flexural strength remarkably in this research. It was especially observed that the use of additives which are listed as polypropylene fiber, flax fiber and crumb rubber in the mortar mixture, can be a very effective method to increase sound absorption performance not only in high frequencies but also low frequencies. As a result, the sound absorption research based on different mortar mixture types in plaster layers were systematically conducted to increase sound absorption coefficients in accordance with the historical building requirements. (C) 2020 Elsevier Ltd. All rights reserved.