Detecting ultrasound, 21-22 khz, 25-65 dB, for last 24 hours

I have been observing some strange stuff going on lately around here concerning RF, EM, and now ultrasound noise everywhere.

I'm no conspiracy kind of guy, but I enjoy reading them, often trying to find some clues or bits of facts, truth, that need explaining.

But, just when they say this cironavirus should be getting bad around here like in NYC, I've begun detecting these annoying quiet to loud ultrasound tones that have been fluctuating a little in frequency, but changing intensity throughout the day.

All last night I monitored this noise, and it was going all night, blanketing my entire house and outside around my yard. It would change intensity, sweeping from just under 30 dB to 65 dB every 30 minutes .. all night long (inside). It would jump in steps, like 30 dB, then 40, then 50, then up to 65 dB. And again, this was inside. It took time to watch this and log a lot of data.

So, I'm wondering, is anyone else detecting or hearing this? I can hear these 21 khz tones myself. The noise reminds me of what I hear coming from the flyback transformers in those old CRT TVs and displays.

If your phone mic is sensitive enough, and fast enough, like a Samsung Note 9, you can download an app called "Ultrasound Detector" and test your environment. You'll need to set the sample rate at 192000 hz. I left the FFT set to 8192. Try with alarm delay set to 0 to begin with. Turn on Keep Awake and Record. Set alarm threshold to 30 dB, then increase if what you detect keeps increasing in intensity.

This is crazy and I can make no sense of it. Most can't hear these frequencies but some can, I can, and my cat can hear it too.

Check your environment. I noticed this in other areas too.