From a comment at the link: "NIOSH does not recommend nor endorse a particular commercial product. The data from our study “Evaluation of smartphone sound meas

From a comment at the link: "NIOSH does not recommend nor endorse a particular commercial product. The data from our study “Evaluation of smartphone sound measurement applications” is available in the journal article referenced at http://scitation.aip.org/content/asa/journal/jasa/135/4/10.1121/1.4865269 http://scitation.aip.org/content/asa/journal/jasa/135/4/10.1... . The discussion section (page 189) highlights two apps — SoundMeter and SPLnFFT — that had the best accuracy over our testing range. There were two other apps — Noise Hunter and NoiSee — that were within ± 2dB of the reference sound source. Once again, note that the data results in the study do not constitute as NIOSH endorsement of any of these products."