How to reduce noise from helicopters/ quad copters
Created 09 August 2013 by Anthony J Williams, born 03.12.1951 Durban, south Africa.
This morning I thought of the following conceptual innovation:
To reduce noise from helicopters, hovering drones and quad copters, create an insulated ‘drum’ surround to the propellers, to absorb the sound of the rotor and rotating propellers, with the exception of the horizontal and vertical sound. All ‘angled’ sound between propellers and ground will be noticeably reduced.
For reduced ‘sideways movement’ wind resistance there is the option of a variety (to be tested) horizontal perforations or sound absorbing blades to the walls of the surround drum, where depth of blade to exceed open width between blades. An advanced feature could allow these blades to adjust to always remain horizontal as the copter angles over. Sound absorbing horizontal blades will reduce all angled sound between propellers and ground, except when copter directly over target.
For minature drone type quad or similar hovering copters, it may not be necessary to have any horizontal perforations or openings in the drum surround, but this needs to be tested. This will slow the sideways movement of the copter through increased air resistance, but will allow a ‘silent’ approach of the copter to its target, for video or whatever other purpose.
The surround sound- insulating drum could also be useful for additional mini cameras, or other purposes such as an invisibility ‘cloak’. The ‘invisibility cloak’ surrounding drum could actually cover the entire copter, body and propellers.
I can imagine the creation of a variety of multi-purpose silent (some ‘invisible’) hovering miniture remote viewing copters being able to navigate outside or inside buildings, through corridors and rooms.