ORIGINAL: dick Hanson
Digesting all the info on that site will take years to really understand it
a simple Radio Shack meter will register all the model noises--close enough for folk music
those who have a formal musical education ,at one time labored thru the basics of first getting a sound -then a recognizable sound - then a pleasant sound --from their first musical instrument
Been there since age 7 -and I started late!
It is not that hard to learn if we disregard sones and fones. The general formula is 10 or 20 times the logarithm from the sound pressure ratio. (10 for vibration, 20 for noise)
Important for us is:
Halving or doubling the noise level is 3 dB(A)
Just hearable difference is 1 dB
The A means A-weighted curve (adapted to the non-linear characteristic of the human ear) This curve is used to evaluate the way people hear noise (or music)
A noise meter for our purpose must be set to slow, and A curve. It need not be very accurate. Most hobby shack meters are within 0.5 dB without ever calibrating them.
Doubling the distance reduces noise by 6 dB (that is why measuring at 3 meters is prone to large error)