I just played my Overton low D for the first time and my dog joined in the music making big time. She doesn’t react to a Dixon low D.
First question: are these howls of pain or are they howls of appreciation.?
Since she doesn’t run away one might think the latter.
Second question: is she responing to inaudible (to us) high notes?
The Dixon has a less complex more pure tone to my ears.
Brian
Well, the one and only time I played a Generation high F every dog in the neighborhood came to my yard…
I haven’t gotten a response from the neighborhood dogs but my cats leave the room whenever I play either my whistle or my recorders. They don’t go as far away when I play the tenor recorder so maybe there is something about the high pitch that bothers them. Or myabe they are just music critics and can’t stand crummy technique!
Chieftain High F…he Loves it
If she comes close to you, sits back and raises her head high, she’s joining the chorus.
If she shakes her head, chases her tail, or hides under the furniture, she’s being aggravated.
Generally speaking. Individual dogs have individual behaviour, of course.
In both cases, I think they respond to overtones rather than absolute pitch, but I could
be wrong. My childhood piano playing might suggest there is an absolute pitch relationship
too, as there was some certain note that easily elicited a chorus.
Once you get enough howling going, you can set off a whole neighborhood… they do it
as a means of identifying one another and where they are. Sort of like a roll call. Or maybe
like checking in at the neighborhood pub and letting everyone know how the wife
and kids are. Something like that.
Don’t let Dazzle know I’m typing this, thats me Chess on the left you know.
That Generation Bb bottom note rattles my teeth but it beats a silent whistle.
Chess
Funny thing is she only did it the first time I played my new whistle. This afternoon no reaction. Maybe its complaining about the new visitor. Come to think of it I think she might have done the same trick when I first got the Dixon.
Brian
My dog must just want to play too, because he gets right up in my face, and tries to take the whistle away from me. (Either he wants to play, or I am just really bad!) 
My dog just loved the bone whistle so much she tried to bury it! 
It sounds like you need to buy a LOT of new whistles and run a scientific experiement.