Check whether the AC adapter might be the culprit.
I realize the AC adapter is outside the computer - if it is near the computer, it is worth a quick check.
Make sure the cord is not wrapped tightly around the adapter.
Open the case and look.
See if you can find what is causing the "buzzing".
The battery might be in the first stages of "inflating".
All batteries die, some do so quietly and some first inflate and then fail.
If the battery is indeed "inflating" a bit, the "buzzing" might be due to one component touching or moving against another.
If it is not the battery,
If the computer contains an internal fan,
The fan might be buzzing due to dirt / dust / wear-and-tear
The information you'll need is in Category > Manuals
Look for the Service / Maintenance guide for your model / computer.
Device Home Page - References and Resources –Learn about your Device - Solve Problems
NOTE: Content depends on device type and Operating System
Categories: Alerts, Warranty Check, HP Drivers / Software and BIOS, How-to Videos, Bulletins/Notices, How-to Documents, Troubleshooting, Manuals / User Guides, Service and Maintenance Guide (Replacement Parts and Procedures), Product Information (Specifications), more
When the website support page opens, Select (as available) aCategory>Topic >Subtopic
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