It may or may not be obvious that the zig zag duct is a lightly damped open ended duct with a smaller CSA than the direct path, and a gain at resonance set related to the ratio of the areas. At the systems anti resonance the difference in path length between the two is some combination pi and pi/2 radians.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
The more I study those charts the less I like them. Y axis needs labelling properly in (A), I assume that is TL. In (B) the total sound power radiated is more important than its directivity, which emphasises the the smallest component of the overall power (but is the nicest curve). Again y axis labelling. I think in this case it is acoustic intensity.
(C) is all over the place. Are the edges of the diagram not supposed to be reflective in the case of a plane wave up the page? How come the intensity vectors cross them in 5900 Hz?
(D) is fine so far as I can tell.
So I suggest if you can't replicate those diagrams then it may be because they aren't very good.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
Sure. But use of 1877 era hand calculations is also appropriate. The spatial distribution is given by 2 pistons in a semi infinite baffle, the resonant characteristics of an open ended lightly damper duct are know, so the combination is all doable.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
