1/3 octave bands are calculated every seconds (or less).
Filters are Class 0 according to the IEC 61260.
You can plug in up to two IEPE powered microphones.
Yes, you can use your expensive Class 1 microphones !
You own the data
The data is stored in open format files, no proprietary software needed.
You also have access to the spectrum values in real-time, on the device or remotely !
The hardware is based on the Raspberry Pi, a 35$ computer.
Add the SonoMKR soundcard (below 200$) and a micrpohone and you're all set.