Noise in the library can disrupt users' concentration and comfort. According to the Decree of the State Minister for the Environment No. KEP-48/MENLH/11/1996, the ideal noise level in a library is 45–55 dB(A). This study aims to design a noise detection system based on the Internet of Things (IoT) that can provide automatic alerts. The system uses a MAX4466 sound sensor and an ESP32 microcont…