Air compressor sound level comparison

Which air compressor is the quietest for your sewage treatment tank? This short video of some rough & ready sound level tests on five 80 litre per second air compressors from leading manufactures that you might find on septic tanks or domestic sewage treatment equipment (Charles Austen, Secoh, FujiMAC, Hiblow & Medo).
Where a sewage treatment tank is near a property, ensuring that the noise level is below audible levels is desirable. It is possible to use enclosures and sound dampening products to reduce noise levels, however it is often best to start by minimising the source of the noise in the first instance.

Results:
FujiMAC R80 38.6 dBA
Medo 80LB 42.5 dBA
Secoh JDK80 43.3 dBA
HiBlow HP80 43.8 dBA
Charles Austen ET80 47.7 dBA

Methodology:
We used the Decibel X v9.2.2 Android sound level app running on a OnePlus10 Pro. While the tests were undertaken in an outdoor / uncontrolled environment, to minimise the effects of changes to the background sound level, the measurement noted down was the minimum each unit achieved over multiple test runs.