The following is a sound file of the noise I hear in my headphones and also on anything I record using two different iMacs and two different PC. The noise isn't subtle; it's loud! This first one was recorded into a digital recorder directly from my headphones.
This is a test afterwards. This was the actual "product". (sorry about the bad lighting) I did hear this noise about a week ago but, but it disappeared so I thought it was a fluke, but when it returned, I figured it's time to give up. Intermittent problems are the worst kind.
Sorry it didn't work out.😢