Basic Physics of Sound (acoustical)

[birds4life]

I work for a museum, and I want to create a sort of "ear trumpet" or reverse megaphone for children to use. The purpose is to show how some animals, like owls, have super hearing. I have a sheet metal manufacturer who can create it. I'm just not sure what the dimensions of the larger hole and the length should be. We want the smaller hole to be quite small (like an inch in diameter) so children simply listen and cannot really yell through it.

Any help would be wonderful. I just want to know what dimensions would be best to demonstrate this concept. Also, this is going to mounted and should be quite large (probably around 2-5 ft in length if appropriate).

EDIT: No matter the outcome of fabrication, this listening device will certainly be safe for all users. It will be positioned in such a way that will prohibit anyone from yelling into the other end.

 

[fss]

Err... this isn't really what you're asking, but have you thought about the liability issues with this? This situation is just begging for some 5-year old to be listening through the ear trumpet while some other 5-year old decides to scream into the other end for fun.