Testing the accuracy of smartphones and sound level meter applications for measuring environmental noise

Abstract

This paper reports on experimental tests undertaken to assess the capability of noise monitoring applications to be utilised as an alternative low cost solution to traditional noise monitoring using a sound level meter. The methodology consisted of testing 100 smartphones in a reverberation room. Broadband white noise was utilised to test the ability of smartphones to measure noise at background, 50, 70 and 90 dB(A) and these measurements were compared with true noise levels acquired via a calibrated sound level meter. Tests were conducted on phones using the Android and iOS platforms. For each smartphone, tests were completed separately for leading noise monitoring apps culminating in 1472 tests. The results suggest that apps written for the iOS platform are superior to those running on the Android platform. They show that one of the apps tested-SLA Lite-is within +-1 dB of true noise levels across four different reference conditions. The results also show that there is a significant relationship between phone age and its ability to measure noise accurately. The research has implications for the future use of smartphones as low cost monitoring and assessment devices for environmental noise.

Beyond the noise: Open source soundscapes - A mixed methodology to analyse, evaluate and plan “everyday” quiet areas

“…With regard to the issue of data quality, (Murphy and King 2016) proved that the measurements apps did a poorer job of accurately measuring at very low background and high noise levels: the latter is a concern given that environmental noise at higher levels is the key area of concern from a public health perspective. Accordingly, in order to test the ability of the Hush City app to calculate noise at different sound pressure levels (i.e.…”

“…The Hush City app is aimed to fill this gap of knowledge in regard to the issue of quiet areas, by: 1) increasing community awareness about the importance of reclaiming and protecting quietness in cities; 2) empowering local communities to map and evaluate quiet spots in their neighbourhoods; 3) impacting on participatory planning processes by training committed citizens in soundscape action research. However sustaining motivation to participate in such studies represents a challenge (Murphy and King 2016): to tackle it, specific measures (e.g. sending newsletters to the participants on a regular basis, publishing new posts on the project's website) will be adopted, following trends in citizen science projects , as recommended in (Nold and Francis 2017).…”

“…Accordingly, in order to test the ability of the Hush City app to calculate noise at different sound pressure levels (i.e. Background, 40 dB, 50 dB, 60 dB, 70 dB), a manual calibration procedure was followed, as recommended by (Murphy and King 2016). A coherent pink noise signal was played over computer speakers and measurements were simultaneously taken by using the Hush City app installed on a Samsung Galaxy A5 and a calibrated sound meter level (NTI XL2).…”

Citizens as smart, active sensors for a quiet and just city. The case of the “open source soundscapes” approach to identify, assess and plan “everyday quiet areas” in cities

“…Murphy and King [51] proved that the measurements apps did a poorer job of accurately measuring at very low background and high noise levels: the latter is a concern given that environmental noise at higher levels is the key area of concern from a public health perspective. In the case of the Hush City app, to guarantee data quality to some extent, NoiseTube's app libraries have been implemented for sound pressure level calculation and calibration [50].…”

“…However sustaining motivation to participate in this kind of studies is always an issue [51]: to tackle this challenge, specific measures have been adopted following trends in citizen science [68]: such as social media engagement and newsletter dissemination.…”