Autonomous noise monitoring system based on digital MEMS microphones: development of a smartphone application for remote communication

Noise monitoring is a useful diagnostic tool for making better decisions in noise control projects and understanding the sonic behavior of a place. Traditionally, sound pressure levels are measured using a sound level meter (SLM), usually for a limited time frame. However, recently much interest has arisen in developing wireless sensor networks that work continuously, especially using cost-effective embedded systems. In this sense, digital micro-electrical-mechanical (MEMS) microphones are a great promise in creating such devices due to their low-cost, high-quality, and integrated analog to digital converter. This paper presents a noise monitoring system based upon digital MEMS microphones and an Arduino compatible microcontroller (Teensy). The system connects to a server through an ethernet cable (providing also a power supply), and sound pressure level data is saved both on the server and an SD card (for redundancy). Furthermore, a backup power supply guarantee that the system continues working even in power shortage situations. The device was deployed in an office and successfully measured throughout a week. Ultimately, the system could be applied to indoor noise monitoring (such as in condominiums and buildings) and used to assess the effectiveness of noise control projects, for example.