Here are few noise spectra of my setup.
Refer only to the solid purple vertical bars the purple line is some sort of max value, but that is affected by where I hold the mobile and my handling, bumping etc of mobile

Where there is a blip around the 7-8kHz mark on some screen shots that's seems to be cause by my fingers pushing the mobile phone screen capture buttons.

Baseline noise inside shed - nothing on.
Average is <40dB
Shedbachground.jpg

Inside shed right next to the WW lathe BMH - yes its pretty noisy, the air "hiss" means it's sucking a lot of air.
An this is why I have to wear muffs when turning
BMHnoise.jpg

The next one down is the spectrum with the mobile in middle of doorway of external DC enclosure with enclosure door open.
Even with the door open this spectrum is likely to be significantly modified by acoustic insulation inside the enclosure.
When outside the enclosure this DC averages about 87dB @ 1m @50Hz
InsideDCenc.jpg

Outside DC enclosure- averages about 65db @1m and @50Hz
OutsideDCenclosure.jpg

Major frequencies are possibly 50Hz motor rumble, and number of impeller vanes x 50 or ~400Hz.

The one thing that this does not take into account is ear sensitivity to frequency.
1kHz is where most people are most sensitive but it can be different for many people.