If you have a vid editing program or even just audio, record it from somewhere and just edit it in.
That’s what i did with TV static for a few of the videos I made.
Yes that would be correct; the idea is that a 1000 Hertz sine wave is the Test Tone used to calibrate broadcasting audio equipment. It’s a solid, non-wavering tone that sits “smack dab” in the center of the sound frequency spectrum, and virtually all audio broadcast systems/stations have this test tone readily on hand to check signal paths (channels).