I've also tried different USB ports and removing all unnecessary USB devices which didn't help. The cable is OK because I've already tried another one and it does the same. I've also noticed that the sound is quite loud but when I move the USB cable, which connects the audio interface to the PC, around and bend it in a specific way the noise gets much quieter but is still there. When I use an EQ to reduce 8000Hz and 16000Hz to -12db the sound is gone. It's just a thin vertical line in the EQ. I recorded a few seconds of silence and when I look at an EQ I can see that the sound is exactly at 8oooHz and another one a little bit louder at 16oooHz. If I turn the gain of the microphone input to the max I can hear it quite clearly. I have noticed that my USB-Interface (Focusrite Scarlett Solo 1st Gen) generates a high pitched sound like a sine wave, actually it generates two.
