Smartphone Sensors for Citizen Science Applications: Light and Sound

In recent years, the continued improvement and deployment of smartphone technology has resulted in the growth of smartphone sensor systems. Citizen science projects that require on-the-spot measurement of a variety of parameters such as illuminance and sound level may benefit from this new technology. As yet, there have been few attempts at critically assessing these sensor systems and their accuracy. I calibrated the light and sound sensors on a variety of apps and on three platforms using professional-grade instruments. Provided that modest adjustments to the recorded data are made using a small set of calibration curves, the usefulness of smartphone sensor light and sound systems for conducting citizen science experiments can be dramatically improved. Light intensity measurements for illuminances above 5,000 lx can be made with ±12% accuracy compared with calibrated values, and sound intensity measurements from 35 to 90 dB can be made to within ±1.5 dB. A significant failing among the light-metering apps is that none of them save the measurements in exportable file formats for later analysis. This greatly limits the usefulness of these apps for non-photographic applications. I conclude that, when proper measurement and calibration protocols are applied, smartphone sensors can indeed generate relatively high-quality data using their light and sound sensors within restricted measurement ranges. These calibrated measurements compare well with professional-grade, calibrated systems, but at far lower cost. This opens the door for a new generation of citizen science and crowdsourced applications involving the monitoring of light and sound values.