I made three phone calls totaling 23 minutes at 2.9 cents / minute = $6.67. I learned that numerous studies have already been conducted to determine the decibel range of many types of helicopters at various distances and altitudes. Or, simply Google “helicopter rotor dB (decibel) levels by type”.
Any illusion that a decibel number will answer the question that the rest of us have already figured out is misguided. Just as different people prefer…