SoundMess Lab

Most sound apps are built for the spike: a big needle, a red zone, a number for how loud the concert was. I wanted one for the work, like reading a room, checking a speaker or watching a decay. So SoundMess Lab is one calm screen: the level up top, and an RTA, FFT or spectrogram under it, a tap apart.

A phone mic is good from about 500 Hz to 8 kHz. Below 100 Hz and above 16 kHz a reading is for reference only, and that's the hardware, not a bug. Most meters never mention it. The shaky ends come out faded, and the info button lists the ranges.

The careful parts are boring on purpose. A, C and Z weighting follow the IEC 61672 curves, and the pink noise is Paul Kellett's filter. RT60 fits a straight line to each band's decay between −5 and −25 dB, the T20 method from ISO 3382-2. A band whose fit isn't clean, or whose decay doesn't stay 10 dB clear of the room's own noise, gets faded or left as a dash.

RT60 also needs a speaker loud enough to fill the room. An iPhone's own speaker can't push much outside the mids, so when that's the output SoundMess Lab measures four bands, 500 Hz to 4 kHz, instead of handing back eight guesses. Connect a Bluetooth or wired speaker and it measures all eight, 63 Hz to 8 kHz. It's a serious listening tool, not a replacement for a calibrated measurement mic, and it says so in Settings.