How to silence Siri read-back through hearing aids on iPhone

I updated my iPhone 17 Pro to iOS 27 and have activated Siri. That's all fine, but I cannot silence the read-back aloud of Siri searches. The read-back comes through my Oticon Real-1 hearing aids, which I don't want, though I do stream other content (phone calls, podcasts, etc.) through by hearing aids. I just want the Siri read-back silenced, because it's sometimes a lot of reading, which is annoying. I've set Siri to "Silent Responses" but the iPhone overrides that because it thinks I'm wearing headphones. How can I silence the read-back of Siri searches through my hearing aids?