I also have several portables (USB 2 & USB 3 ranging from "old" 500gb to "new" 1.0 & 2.0TB) none of these have the problem.
I also use these portable HD's on several PC's using VLC & Windows media player. Both PC's use "on board" sound, is this the same with your set up? or are you using installed PCI "sound cards"?.
As mta asks what models, types, connectivity etc. may give one an idea
What programs are running in the background? I only ask because years ago when uTorrent was downloading it would cause an small audible noise/interference through headphones while listening to music.
Firstly We are using brand new 2TB seagate Hard drives bit over the top But we have a huge cd collections and we trying to convert everything to flac files. We have Two Maxell 500 Gb hard drives as well .
After painstakingly writing our whistle problems out and then copying and pasting what I originally wrote into open office for spelling correction because for the life of it we can not get Firefox (37.o.2) to show spelling mistakes Then proof reading it when pasted in to forum then we decided to delete it and start again because we carried out further experiments checking leads. Still 3 laptops are all have the Heterodyne whistle when placing the music file into VLC or WMP.
I stated That we copied and pasted a music file to the desktop and this seemed to do the trick. But did not still tell us why we had a whistle. We are fascinated to know how many others have it but for one reason or another have never noticed it. Can we reiterate please that if you give it a bash. to see. Please use headphones to listen.
Ok: further developments your going to love this. After we closed down and turned this computer of my Sister was on the other computer. using Firefox browser 37. .0.2 In case anyone asks or its of importance. On you tube we of headphones running the New asus notebook we use as a google chrome device through Panasonic TV HDMI Cambridge Dac Magic into Roksan k2 amp and monitor audio S1 speakers . Hayley clicked on the video and the Heterodyne whistle started as the video loaded It was the same whistle we are getting on all three computers No hard drives in use this time. Interesting problem To say the least
When things you think could not get more puzzling , transferd a couple of songs to mini disc via the hard drive and Cambridge Dac and Low and behold The mini disc finds the whistle audible to record and you hear that same Heterodyne whistle at the start and the finish of the track and if your aware of it on quite songs you can hear the whistle all the way through.
Its not the Dac magic we eliminated by process of ilimination as the Dac does not get moved around from computer to computer
nothing running in the background only windows explorer Andavari
usb both 2TB are mains powerd maxell 2.0 usb Asgandy
nothing running in the background only windows explorer Andavari
Impossible to having "nothing running in the background" on a Windows computer. The noise you hear can/may be caused by any running program such as an anti-virus which is literally always scanning and can be heard through headphones on some computers as a low-level whistle, etc.
Although it may not be something running causing it - it could be the hardware, etc. For instance I moved my soundcard from one slot in my tower into a different one to stop an interference sound.
Edit:
Something I forgot is some manufacturers will have the headphone plugin and USB inputs shared as one unit on the front of a computer, having a USB device plugged in while listening through the headphones can cause a noise in the headphones especially if the USB device is doing something like copying files to from it, etc.