I have been digitizing my LP collection off and on over several years. I have an old audiophile turntable - pre-amp - INPort - laptop setup. The INPort box converts the R&L turntable/pre-amp outputs to USB output. I used the software supplied with the INPort for several years, but it no longer works.
Recently, I’ve been using Audacity 2.0.6 on an older laptop (Windows 7 Pro 64-bit) for the recordings. The only processing I’ve done is to remove clicks and normalize. When I play the files on the older laptop they sound fine. When I play the files on my primary laptop (also Windows 7 Pro 64-bit) I’m getting a high-pitched squeal in the background. I’ve listened to the various “hum” and “buzz” recordings people have posted, but this has a higher pitch. The sound reminds me of a car engine belt that’s slipping. I’ve tried both copying the Audacity project files and various other export formats (mp3, mp4, wav, aiff) (exported from the older laptop) and get this squeal on my primary laptop regardless of the format. I’ve played the files in various players (Audacity 2.0.6, iTunes, Windows Media Player, VLC Media Player) and through my primary laptop speakers and earbuds. I still get the squeal on my primary laptop. I’ve read about grounding issues: both laptops are plugged into surge protectors, then grounded wall outlets (US) in different rooms.
The laptop tech support folks checked my sound driver and played with settings, but they only made it worse because now my primary laptop won’t even recognize the INPort. The music that I digitized using either laptop and the old INPort software still plays fine, no squeal.
Does anyone have any other ideas I should try to eliminate this squeal?
Man! That’s hard to read with all of those thoughts jammed into one paragraph! 
When I play the files on the older laptop they sound fine. When I play the files on my primary laptop (also Windows 7 Pro 64-bit) I’m getting a high-pitched squeal in the background.
So… This has nothing to do with the INPort, Audacity, or recording… it’s a playback problem, right??? You have the same issue with all audio files (including the ones you didn’t record yourself) and with CDs, right?
I’m getting a high-pitched squeal in the background. I’ve listened to the various “hum” and “buzz” recordings people have posted, but this has a higher pitch.
That’s probably just “digital noise”. There are LOTS of digital signals inside a computer, and audio quality is often an after-thought.
I’d try a USB soundcard. (For playback, not to replace your INPort.) Taking the soundcard out of the noisy digital environment can often solve the problem. This doesn’t always work because there is sometimes noise on the USB power supply and some USB soundcards are sensitive to this. But, it’s probably worth a try.
Sorry the problem wasn’t clear; I put returns into the text when I typed it.
This is not only a playback problem.
I do NOT get the squeal on all audio files. The files (1) I made before using Audacity or (2) from CDs I’ve transferred to the hard drive or (3) that I purchased from iTunes store do NOT have the squeal.
I ONLY get the squeal on recordings I made with Audacity either (1) on my primary laptop or (2) on the older laptop and copied to my primary laptop. I do get the squeal when using various players on my primary laptop.
I purchased this laptop with all the gamer sound technology upgrades (Realtek high definition audio & Onkyo speakers) so audio quality was probably not an afterthought.
So it sounds like you need to address that INPort software issue. Why does the old software no longer work on the same operating system? What do INPort say about it?
Gale