In a piston aircraft, how much noise is generated by the engine, and how much by the propeller? I've been reading quite a few articles lately about how noise complaints from GA airports across the country.  One of the common suggestions to fix the issue is to simply use an electric engine instead of a gas powered one.

Leaving aside other practical concerns (batteries and weight for example), would this actually significantly reduce the amount of noise a GA aircraft makes?  I'm told a lot of the noise actually comes from the propellor itself, not the engine.

So, in essence:  How much of the noise from a GA aircraft is made by the engine, and how much is the propeller?  And does the percentage change depending on the phase of flight?



Note: I am not asking for subjective answers here.  My hope is that someone actually has a decibal break down of how much noise comes from the engine, and how much from the propellor.  Yes, I know it will vary by craft.  An average would be fine, or perhaps numbers from a popular GA craft (like a Cessna 172 or Piper Cub, for example.)
One particular example I can recall is Extra 330. Modification with electric engine have been built (Extra 330LE) keeping the rest of the aircraft quite similar to the original petrol-engine version as far as I know. According to this article electric version was measured to produce 14.5 dB less noise compared to the combustion engine aircraft.

Maybe you can try too look for other combustion engine aircraft converted to electric without making other significant modifications (I am not aware of any other than this Extra 330LE though) as a source for data you are looking for.