It doesn’t need to be a confrontation - just have a chat with your manager, mention that you have an ADHD diagnosis and that you have been recommended some things to help improve your focus, attention and performance at work, and that one of those suggestions was listening to music or white noise through headphones, and ask if it could be considered as an adjustment due to your disability. If you frame it as a collaborative and positive action that you can take together, rather than something you’re demanding to be different, I don’t think there’s any reason for your manager to be offended by the request.