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User profile for user: BogdanAlexander
BogdanAlexander Author
User level: Level 1
11 points

Loud buzzing noise in external audio when connecting my MBP to an external monitor using USB C

When I connect my MacBook Pro (15-inch, 2019) to the external monitor, a Dell U3818DW,

using USB C there is a loud cracking noise:

  • In the 3,5mm Headphone jack
  • In the sound of any external USB sound card.

The noise color changes depending on windows on the external screen.

Sometimes it disappears for a while, but it's there most of the time.

The noise is there in the speaker even when the USB sound card is turned off.

It doesn't matter if the power comes through the USB C from the monitor

or from the Apple power adapter.

It disappears the moment I unplug the monitor.

Workaround:

There is no noise if I connect the monitor using a USBC - HDMI adapter.


MacBook Pro 15″, macOS 11.1

Posted on Jan 14, 2021 8:36 AM

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User profile for user: katesdad
katesdad
User level: Level 1
4 points

Posted on Jan 25, 2021 10:17 PM

I have the same problem. I've tried everything to isolate it and it comes down to the external monitor. I have been using a USBC to HDMI adapter - even tried a different adapter - and the humming noise is still there.

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User profile for user: Grant Bennet-Alder
Grant Bennet-Alder
User level: Level 10
133,171 points

Jan 14, 2021 8:54 AM in response to BogdanAlexander

Conventional wisdom about buzzing Audio is that it can be caused by ground loops. Ground loops are caused by powering different equipment on different circuits that have ever-so-slightly different earth/grounds. That causes a tiny flow of electricity that gets into amplifiers and gets boosted up into buzzing.


The solution to THAT problem is to connect all the Audio equipment to the same circuit, making sure everything is propel grounded, or connect the grounds together so they can not be different.


Once you have eliminated that, you can pursue other issues, if any.

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Loud buzzing noise in external audio when connecting my MBP to an external monitor using USB C

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