After the latest Windows Update, my speakers are NOT muted when I am listening to my headphones.
IIRC, it used to be that if I was playing something on my laptop speakers, when I plugged in my headphones the speakers would automatically mute. Twenty years ago this was done with hardware. More recently in software. Then a few years ago, Microsoft changed this behavior and created a separate headphones device that was, I believe, exclusive from the speakers. The windows default device was changed whenever you plugged (or unplugged) your headphones. (Curiously, stereo mix would work off the speakers, but not off the headphones.) In the most recent Windows update, Windows 10 Home, version 2004; OS build 19041.610; Feature Pack 120.2212.31.0, this behavior changed undesirably.
The new behavior is that the headphone device has been removed. The headphones work just fine when they are plugged in. The problem is that the speakers do as well. And if I mute the speakers the headphones get muted, too. Other than just annoying, this can cause problems when overdubbing.
When I searched on the internet for solutions to this problem, I found several reports of this happening, ranging from a few months ago, to over a year ago, so this appears to be an ongoing problem for Windows users. There were no obvious solutions offered, only a suggestion to update drivers, which almost seems counterproductive.
I went to https://support.hp.com/us-en/drivers, then clicked on the laptop icon. When prompted for my serial number, I entered “15-bs060wm” which is my HP Model number. I clicked on “Driver-Audio(7)” and was presented a list of seven(7) Realtek High-Definition (HD) Audio drivers. I started downloading and installing each one starting with the latest (June 2020). The first 3 failed with the message “Not Supported”. However, the Dec 27, 2019 (6.0.8734.1 Rev.A) (sp93151.exe) worked. It did take two reboot cycles - I suppose the first reboot was to uninstall my old driver. My output device is now called “Speaker/Headphone”. It plays out of my speaker, then mutes the speaker automatically when I plug in my headphones. And unlike before, “Stereo Mix” seems to be available even when the headphones are plugged in. I am one happy camper.