The implementation of low-cost urban acoustic monitoring devices

Abstract

The urban sound environment of New York City (NYC) can be, amongst other things: loud, intrusive, exciting and dynamic. As indicated by the large majority of noise complaints registered with the NYC 311 information/complaints line, the urban sound environment has a profound effect on the quality of life of the city's inhabitants. To monitor and ultimately understand these sonic environments, a process of long-term acoustic measurement and analysis is required. The traditional method of environmental acoustic monitoring utilizes short term measurement periods using expensive equipment, setup and operated by experienced and costly personnel. In this paper a different approach is proposed to this application which implements a smart, low-cost, static, acoustic sensing device based around consumer hardware. These devices can be deployed in numerous and varied urban locations for long periods of time, allowing for the collection of longitudinal urban acoustic data. The varied environmental conditions of urban settings make for a challenge in gathering calibrated sound pressure level data for prospective stakeholders. This paper details the sensors' design, development and potential future applications, with a focus on the calibration of the devices' Microelectromechanical systems (MEMS) microphone in order to generate reliable decibel levels at the type/class 2 level.

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

“…Taking into account these technical microphone's features and a large number of inverse filter coefficients, we concluded that a costly inverse filter of the microphone's frequency response cannot be implemented on a system with limited resources, and it is not necessary for the Category 3 device, as classified in [21]. The calibration of the final sound level meter is sufficient and this has been also confirmed by the results in Section 5.…”

“…The results of 12-minute measurements in the indoor environment showed that the proposed sensor node closely follows values registered by Class 1 Sound Level Meter with the mean difference less than 2 dB. Thus, according to [21], the proposed solution belongs to the Category 3 -Low-cost sensor network, which consists of custom-made nodes designed to be inexpensive, low-power and autonomous for large-scale deployments. The proposed sensor node is a promising and viable solution for measurement in application scenarios where legally enforceable sound level data are not needed but measurements are sufficient for informative screening of noise levels.…”

“…Mydlarz et al in [21] present the design and experimental measurements using a low-cost MEMS microphone. The measurements performed in this study show that analog MEMS microphone solution is suitable for accurate urban acoustic monitoring.…”

“…Also, the sensitivity of MEMS microphones varies very little over temperature, a fraction of a decibel at most [28]. However, Mydlarz et al in [21] used sine sweep method to create the impulse response of the MEMS microphone mounted on the PCB. They showed that when the microphone is mounted on the PCB, unwanted effects and resonance (i.e.…”

Seeing Sound

“…One of the potential applications of the Audio-Annotator tool is to annotate sounds captured by an urban acoustic sensor network [34]. Therefore, we based the audio stimuli on soundscapes of urban sound events related to traffic, construction and other types of human activity.…”