Why does Audio fade-in instead of starting at set volume level?

• Ubuntu 18.04.01
• HDMI from GPU to the Asus monitor speakers (volume set to 100 within the monitor's menu)

When, for example, I start a YouTube video the video starts playing but, the audio slowly comes online. That is, it goes from zero volume and slowly progresses, fades-in, up to the volume I actually have set (about 50%). It's like there is a dial being turned.

Instead, I'd like the audio to immediately come online when I start a video at the volume I have set.

Audio works fine otherwise, it's only when it starts that it transitions in slowly. Happens every time I pause and play a video again. Audio slowly comes online.

Not sure what would cause this. I checked monitor for settings and it only has the volume. I checked Ubuntu sound settings and don't see anything there. I checked in YouTube as well Firefox settings and see nothing there either. Not sure where else to look. I also checked out alsamixer too.

I think this is due to pulseaudio suspending the respective audio interface, presumably for power saving reasons.

Try editing your pulse audio config (for me /etc/pulse/default.pa) and comment out this line to disable this feature:

load-module module-suspend-on-idle

Then restart Pulseaudio:

pulseaudio -k