Why do my homepods suddenly increase volume mid-song on tracks that aren't Dolby Atmos?

I've noticed this issue since I purchased my second gen Homepods. When I'm listening to songs that aren't Dolby Atmos, sometimes the volume will increase while the song is playing. The actual volume I have set does not change, but the song will be playing and suddenly it will be significantly louder. If I restart the track or skip it, the polume will drop back to normal. It increases roughly the same as if I had raised the volume by 10 percent, but like I said my actual volume setting does not change at all, just the actual volume of the audio. Turning off Dolby Atmos doesn't affect this behavior. Has anyone encountered this?