Audio levels sometimes take a momentary dip in volume

[MPivot]

I have noticed, in both my vehicle and on my earbuds (both connected via bluetooth), that the audio sometimes take a momentary dip in volume. I could understand if this occurred between tracks of music, but it is not. Instead, when I notice the issue, it is usually in the middle of a track. Sometimes, it happens multiple times within the same track.

Has anyone noticed this?

 

[TabGuy]

This will happen when a notification arrives and you have notification volume set to zero. It acts like it's sending a notification sound but you don't hear the sound.