Figure 2: A-weighted app-based measurements were compared to A-weighted measurements made using a calibrated Type 1 sound level meter (SLM). In the A-weighted condition, SoundMeter was highly consistent across conditions, with measurements being within 1-2 dB of the calibrated Type 1 SLM. dB volume was accurate within 1-2 dB at levels up to 80 dB at 1, 2, 4, and 8 kHz. At 250 and 500 Hz, and at 1, 2, 4, and 8 kHz frequencies when levels were above 85 dB, dB volume sound levels were reported as 5-10 dB lower than that measured using the calibrated Type 1 SLM. The other apps, advanced decibel, SPLnFFT, and SPL, consistently reported levels that were elevated relative to the SLM, with differences ranging from 3 to 10 dB across frequencies and levels for each app. Nonlinear errors were observed at presentation levels above 85 dBA for dB volume, advanced decibel, and SPL apps. Data are mean ± standard deviation