High Frequency sound followed by strange occurences

I don't know if this qualifies as "the hum" as many describe in this forum, but I honestly don't know where else to share this experience... I go outside pretty much every night to stargaze and enjoy the serenity of the night. I live in a relatively rural part of Alabama and am accustom to the normal sounds of crickets, frogs and other wildlife in the area. On at least a dozen occasions over the past 3 years I have been listening to the sounds of crickets chirping and it's as if the noise of the independent crickets become merged into a louder, higher frequency sound that is obviously very different than the natural one. This alone wouldn't be enough to alarm me, but at the same time orbs often appear in the woods surrounding my property - hovering above the tree line usually. On 2 of those occasions my dog has gone nuts, started growling and ran off barking into the woods towards the direction I am hearing the sound emanating from. I also get this feeling of being watched and just an eerie feeling of "something not being right". The "hum/buzz" is so pronounced it's like I can feel it in my body. Almost like I'm vibrating internally in response to it. It lasts anywhere from 5 to 20 minutes and always happens between midnight and 3am. I have no explanation for this and am just seeing if anyone else has ever experienced anything similar.