The Loudness Control option in the Sonos App for a room/zone is typically not required to be active. Loudness by definition is really only needed to boost bass and treble frequencies when listening at low volumes.

Therein lies the conundrum (so to speak) as “listening at low volumes” can be subjective based upon one’s preference and/or hearing.

The best way to determine if “Loudness” should be active is to listen to your music at YOUR preferred level and toggle the Loudness on and off to see if there is a noticeable difference. It’s been my subjective experience that the “loudness” option extenuates frequencies to a level just below distortion at my prefered listening level. Therefore, Loudness is off for all my rooms/zones.

Try toggling Loudness on/off to determine your preferred setting.