Its actually pretty interesting. Ive got one of those decibel meters in my phone too.
The loudest sound Ive gotten so far is a rock breaker on a excavator 115db.
R22 hovering at about 50ft away 99db
44 " 101db
EC120 " 86db
Havent got a JR yet.
I think that sometimes its not the level of noise, but the perception of the noise.