Laws will vary by jurisdiction and there may be exceptions or less restrictions for engines manufactured prior the passage of the latest statute. 75-80 dBA at 50 feet would be considered quiet in most states.
Scroll down to related links and look at "Conversion Voltage V to voltage level Lu and LV - Decibel (dB) level conversion to volt ".
Yes.
convert signal gains or losses to comparative decible reading.
A: Dbm or decibel of modulation
Scroll down to related links and look at "Conversion of sound levels".
No. It's the log of the ratio of two power levels. It a magnitude without a direction.
Typical sound levels are kept under the 125 decibel pain threshold, otherwise people would leave.
On what exactly? if on a stereo or TV, turn it down, or turn down the bass/tremble.
Audio perception of intensity of sound. Every additional 3 decibels represents a doubling.
You may first want to try talking to your neighbors to address the issue. If that fails, you can check your local noise ordinances to see if they are violating any laws. If they are, you can file a noise complaint with your local authorities.
I dont know, but it is legal to drink on a boat in Wisconsin.
What are the uses of DECIBEL?