South beach sand, particularly in Central Java, Indonesia, has a smooth texture that distinguishes it from other types of beach sand. The purpose of this study is to identify the properties and sound absorption coefficients of beach sand. Previous studies have found that beach sand in the yard of the Great Mosque of Surakarta is a component of the courtyard that absorbs the high sound. Subsequently, sand performance measurements were performed in the laboratory to assess the material's ability to absorb sound using the metrics of reverberation time (T30), Sound Transmission Class (STC), Outdoor-indoor Transmission Class (OITC), Noise Reduction Criteria (NRC) and sound absorption coefficient. According to the test results, south beach sand has an absorption value of 63%, which is comparable to that of other natural materials, such as wood. The findings of this study can be followed by simulating the use of south beach sand in other mosques to create a calm and quiet atmosphere.
