Electrical Buzz Audio Problem

[Kaseli]

We have a USB splitter that connects an external hard drive to two separate computers (MacBook Pro and an HP Laptop). Unfortunately, the USB splitter is emitting an electrical buzz that is picked up in audio recordings on the MacBook Pro only. When the external hard drive is connected directly to the MacBook, there is no buzzing noise picked up on the MacBook and the audio quality is perfect. However, when the usb splitter is added back in, we get the electrical buzz again. Any thoughts on why this is happening or why this is happening only on the MacBook Pro?

 

[Lawrence_SoCal]

Without a clustered file system, you risk data loss connecting a single USB drive to multiple computers, last I recall.
A USB switch, so that only 1 computer connected at a time would possibly be okay. but a splitter is risky is typically strongly recommended against.
as for buzz, typically means a grounding issue. So I'd guess an incompatibility between USB splitter and Mac, probably due to low-quality splitter (but only guessing).

 

[Kaseli]

It's a switcher not a splitter

 

[Lawrence_SoCal]

Ah, good to hear
As for noise/incompatibility, same likely cause as mentioned earlier (doesn't matter is switch/hub/splitter)

I'm NOT an electrical engineer... so take this for its worth
You could try a higher-quality USB cable from Mac to splitter, with some ground loop isolation protection built-in? or maybe changing power plug-in circuits (maybe outlet, maybe circuit)? Maybe using a different port on the Mac and/or splitter?