Glen, seeing IS believing,but ........ just gotta say that I have never heard a hog make a sound exactly like the sound produced by that Hydell caller. Specifically ... the "rattle" sound. My deer grunt tubes produce more of a lower tone. None of the "rattle" like sound.
Hard to explain,however I would not really classify the sound that you were producing in the vid a "grunt". I do realize that it works,and bottom line is,if you played Michael Jackson music and the hogs responded to it that would put the hog on the ground.
I have purposely wrapped some of my calls to produce a lower tone,a deeper grunt,and to take out all the "rattle". I have called in some hogs,however I just might need to "rethink" my calling techniques and/or sound produced.
Thanks for the learning tool that you have chosen to share with us. --- pruhdlr