Noise Management

Being aware of the noise we create with our models and continuing to manage those noise levels to as low a level as possible is what we should all be trying to do as good, responsible members and Dave and Lenny have put together the following guide to help us do so (thanks guys!)

Noise in Model Aircraft and methods of reducing noise

by Dave Lucas and Lenny White

Scientifically speaking noise is vibrations in the air or water ! By putting measures into place we can reduce the noise levels of our models. Excessive noise/vibration in our models comes from the following and the below is not necessarily in order.

  1. Inadequate Silencers. The dustbin Silencers sold with some brands of engines do not contain any baffling or very little and are lacking in effective silencing volume and just give enough back pressure for the engine to run properly.
  2. Propellers. The glass filled propellers with the exception of APC are the noisiest followed by wooden. Correctly sized Carbon Props are the quietest.
  3. Induction noise. Air getting pulled through the carburettor.
  4. Airframe noise. Loose ancillaries like wobbly wheels, loose covering.
  5. Some Petrol engines have thin cooling fins and can vibrate.
  6. Flying Full throttle for the duration of the flight.

Measures you may be able to emply to reduce noise in some of the above:

  1. Invest in an effective silencer with good baffling and plenty of volume. There are plenty of after market effective silencers out there, either cannister or tuned pipes.
  2. Though more expensive, Carbon Props are far quieter as they are much stiffer than glass filled and wooden props. Also, 3 blade props are very quiet as you are going smaller in diameter thus reducing the tip speed compared with a 2 blade equivalent. A bench mark would be to choose a 3 blade would be to go down one on the diameter and up two on the pitch. Last thing on props... keep them clean and regularly remove all dead flies.
  3. If you can choose a rear induction engine go for it as you can draw the air in from the fuselage.
  4. Make sure all the wobbly bits on your airframe are nice and tight and secure. For example, Wobbly wheels - bush them.
  5. Run your finger nails up and down the cooling fins on the cylinder head(s). If they make a ringing noise pack all the corners with rubber tubing cut to say 5mm long. Then run your finger up them again to hear the difference.
  6. Throttle discipline. There is no need to fly full throttle for the duration of the flight. Only use enough power to keep the model at your chosen height and use extra throttle appropriately, eg. for climbing. You never see full size aircraft flying full throttle for the duration of the flight unles it is red bull air racing!

Remember, flying sensibly and appropriately as well as making the effort to quieten your models will avoid issues and allow everyone to enjoy our hobby to the fullest.