Question: This is the weirdest issue I've ever encountered with my PC. Every so often, my sound will start playing back at a lower volume. This happens when watching video, listening to music, all independently.

It usually lasts anywhere up to a minute, after which it will turn up again.

The weird thing about it is that the volume control in Windows remains at 100%, even though the volume is audibly a lot lower. (No, I'm not going deaf, it's just my PC. I checked.)

I just have no idea where to go to troubleshoot this, even.

I'm using Windows 7 64-bit with an on-board Realtek sound-card.

Oh, just in case someone finds this question on Google or whatever, making sure this is on Do Nothing may fix your problem. Unfortunately, it did not work for me.

![Windows Sound dialog](https://i.stack.imgur.com/vwEgV.png)

My settings all seem fine. This is my audio slider. (Took the screenshot while the issue showed.)

![enter image description here](https://i.stack.imgur.com/1AHLD.png)

Answer: 
It could be a Steam setting that lowers your system volume when you get a message. 

Turn it off in your Steam settings.
For me, the problem was solved by running Windows Update followed by ensuring the drivers for the audio / video card AND the chipset were up to date.