Is there any "chisaran" (is there something "lacking") in one's fulfillment of the Mitzvah of Talmud Torah if they listen to soft, slow paced, instrumental music (no vocals or lyrics) while learning in order to focus better or drown out background noise?
The best way to learn Torah is aloud. That means that we should be listening to our learning.
I wonder whether you can learn aloud if there is background music. In my experience background music is useful if you are studying quietly.