If you haven't used a db meter to measure, you might not realize the difference. A drop of 3 db on the meter cuts the sound pressure in half. Your ears can only detect a drop of 10db or more. Do to an issue at the park where we fly regarding birds, we were forced to do a lot of sound measurements on combat planes. A modern F2d engine turning 30K is below 86db at 10 meters and below 90 within a foot or two. The background noise from the freeway at the flying field is 86+db even with light traffic. We tried to measure the combined sound pressure from two F2D's flying a match but the sound 20 ft outside the circle was below the "background" level of 86db. A lot of the noise on our engines comes from the propeller and the intake. Ever heard a 1/2A electric pylon racer? they are almost silent without a propeller, but with a 4 1/2" prop turning 40,000 RPM they are louder than a Cyclon .049. If you're launching loud airplanes it's always a good idea to wear ear protection. A normal conversation is in the 60db range and above 85db causes hearing loss according to OSHA.