Figure 3: The difference in means is shown for frequency by level conditions. We calculated the average measured level across the 20 measurements with the sound level meter (SLM) made for both the C-weighted (a, c, and e) and A-weighted (b, d, and f) conditions, and subtracted the average SLM measurement from each individual measurement. In some cases app-based errors exceeded ±10 dB. Only one app, SoundMeter, was accurate within 5 dB across all frequencies and levels for both C-and A-weightings. Data are mean ± standard deviation