Accurate Indoor Sound Level Measurement on a Low-Power and Low-Cost Wireless Sensor Node

Abstract

Wireless sensor networks can provide a cheap and flexible infrastructure to support the measurement of noise pollution. However, the processing of the gathered data is challenging to implement on resource-constrained nodes, because each node has its own limited power supply, low-performance and low-power micro-controller unit and other limited processing resources, as well as limited amount of memory. We propose a sensor node for monitoring of indoor ambient noise. The sensor node is based on a hardware platform with limited computational resources and utilizes several simplifications to approximate more complex and costly signal processing stage. Furthermore, to reduce the communication between the sensor node and a sink node, as well as the power consumed by the IEEE 802.15.4 (ZigBee) transceiver, we perform digital A-weighting filtering and non-calibrated calculation of the sound pressure level on the node. According to experimental results, the proposed sound level meter can accurately measure the noise levels of up to 100 dB, with the mean difference of less than 2 dB compared to Class 1 sound level meter. The proposed device can continuously monitor indoor noise for several days. Despite the limitations of the used hardware platform, the presented node is a promising low-cost and low-power solution for indoor ambient noise monitoring.

Low-Cost Sensors for Urban Noise Monitoring Networks—A Literature Review

“…Although the sensors were designed for indoor use, the network presented in [38] in 2018 can be detailed here, since such device could be adapted for outdoor environments. In their paper, the authors use an analog MEMS microphone (SiSonic TM SPM0408LESH-TB) with an analog amplification gain of 20 dB, mounted on a MCU (ARM 32-bit Cortex STM32F050K6U6A, STMicroelectronics), while the sink node is carried out using a PC-based system on a R-PI with a ETRX357 ZigBee module.…”

“…It therefore seems interesting to make a detailed point of current research on this subject, and in particular to highlight the essential characteristics that must be considered for this new generation of acoustic sensors in order to respond to the identified issues and the future ones. Compared to recent articles that already present a review of the existing system [35][36][37][38][39], the present contribution focuses on a detailed analysis of the technical solutions developed in the literature, highlighting their strengths and weaknesses, and showing how the rapid evolution of technologies can now fully meet the requirements for a successful deployment of modern noise SN.…”

A power-efficient audio acquisition system for smart city applications

“…In recent years, many research works involve wireless sensor networks for acoustic noise collection [8,9,10,11,12,13,14,15,16,17]. Their main focus is the development of systems that have low enough power to reliably operate with little to no human intervention.…”

“…The work in [9] presents a node that collects audio level information as well as other types of data. It is designed to wake up based on a timer interrupt or when the accelerometer is triggered.…”

“…This will be compared to the Zigbee standalone implementation in this paper since it has the lowest overall power consumption. When looking at the work in [9], the average power consumption claimed is 45 mW. This is based on a periodic interrupt to transition from sleep to active, a common technique used to save power in such systems.…”