In my case, it seems to add a little focus to the sound. Waves are bouncing in the room everywhere, so there could be multiple effects, for example, blocking waves from the back. I have two chairs, a low one, and another with a high back support that extends around and above my head. This last one probably blocks some of the waves bouncing from the back and to a lesser extent the side walls. If I sit back in the chair, the sound gets muddier. With a tube-like cushion behind my neck it sounds ok.
View attachment 142647