Effect of smartphone orientation on sound level measurement

The proliferation of smartphones provides an opportunity for acoustic measurements to be made by citizen scientists. However, there are concerns about the accuracy of data collected by the public. This study reports on the variability in smartphone sound level measurements due to how the device is being carried. A sample of smartphones running either Android or iOS and with various microphone placements were selected and calibrated for dBA measurements. These devices were tested in anechoic and semi-reverberant rooms while being situated to reflect common carrying positions. We found that the measured sound level in the anechoic chamber could vary by >10 dB depending on the orientation of the device, the location of the microphone, and the relationship of the device to the sound source. Smaller but still substantial variation was observed in the semi-reverberant space. These data highlight the variability probable in participatory sensing efforts, and underscore the potential usefulness of providing guidelines for data collection by citizen scientists. [Work supported by the Battelle Engineering, Technology and Human Affairs Endowment.]