Substances

[Tangles]

Interesting question MJ. I am profoundly deaf and never thought about whether others can actually hear drones - are they noisy?
I suppose if one was defending them you could ask whether they are anymore likely to spook a horse than say a crow or a seagull?

http://www.telegraph.co.uk/news/2016...ck-and-wilfli/
http://www.thedailybeast.com/article...my-drones.html
http://www.beefcentral.com/features/...-of-the-myths/
some sites of interest