Some recent studies suggest that some smartphone applications may be able to measure noise as precisely as a Type 2 SLM.[15][16] Although most smartphone sound measurement apps are not accurate enough to be used for legally required measurements, the NIOSH Sound Level Meter app met the requirements of IEC 61672/ANSI S1.4 Sound Level Meter Standards (Electroacoustics - Sound Level Meters - Part 3: Periodic Tests).[17]