I rarely find that I need any English speech subtitled even in very strange variations,my bugbear is the telephone. Phones have a limited frequency range and lose for me some of the tones that help me understand what is being said.The other problem is of course seeing the face of the speaker,looking at a face you can see without realising it many clues such as emotion,all the little things that help you understand what is being said, and whether the speaker means what they said.