[RWebb]

dB - not db or DB or Db

the reason is that the B means a Bell

and the d means deci-

yes it's a log scale

there is likely a real pretty graph with icons for various examples on the internet somewhere

it may have more annoyance impact than the increment from 36 to 39 tho - depends on location of listener & source + any reflective or absorptive surfaces in the area (not to mention standing waves)