Generally, it’s best to have the field playing within your aura, which–for most people–is an agg-shaped area around the body that extends about as wide as your outstretched arm.
Unless you have an exceptionally well-developed aura (or are of dramatic height or of unusual proportions), “across the room” is probably too far away for optimal use.
That being said, according to the Official Sapienmed FAQ (Updated), when your field is playing within your aura, that’s sufficient to get best results. You don’t need to put your speaker right next to or in your mouth.
If your field is playing with your aura and you want to get “more” out of your field, then you can use the tips in How to Better Connect with Servitors/Audios/Items/Mandalas.