Pulled as an example from a personal collection of high-frequency interference recordings made with a Radioshack Telephone mic (I love those little buggers!) via a Sound Devices 702 and Barcus Barry pre-amp. The original was recorded at 192kHz / 24bit. This example was pitched down 4 octaves before being sample rate converted to 48k/16bit. The source was a goose-neck lamp at my bedside. Check out the original non-varispeed version at https://soundcloud.com/soundeziner/48khz-interference

The high wavering tone you hear was originally between 46kHz and 62kHz. Your dog would love it.