This is sometimes called the “cocktail party problem”, or more formally “Blind Source Separation”. It’s tough, especially with one or two sensors. You’d also ne

This is sometimes called the “cocktail party problem”, or more formally “Blind Source Separation”. It’s tough, especially with one or two sensors. You’d also need a fairly unobtrusive way to choose the source, which is also tricky. That said, I had a classmate with a hearing impairment. His device had a tiny wireless microphone that preferentially fed his hearing aid (I.e., he could hear other stuff too, but the mic was loudest). The teacher usually wore it, but it would be given to you if you were working with him on something. It was certainly a little clunky, but it did seem to help him a lot. Perhaps something similar could work for your dad? Unfortunately, I have no idea what the device was called—and it was a long time ago- but maybe this is enough of clue for his audiologist.