I ware hearing aids because I'm deaf to high pitch sounds, I can't even hear birds singing without them. I went out sometime ago and forgot to take the aids out before I left and I too heard a slight whining noise that I had never heard before. I think it's normal and nothing to worry about, I don't.
If it really bothers you I suggest you ware ear plugs. Sorry if that sounds sarcastic, I don't mean to be but even I with my deafness find long rides with ear plugs far more comfortable and they will help protect your ears. The moulded to your ear type are the best, I've tried lots of different types and they are more comfortable than the throw away type and quieter.
PS my deafness was not caused by riding but shooting etc with the army.