Maybe you are misunderstanding the figure of speech Jesus is using. When I request my son to put away his video game and tidy his room, he hears me, but does not want to obey. So, he ignores me. If I come in every five minutes to check on progress, and repeat my request, but he does not want to leave his game and comply, he still hears me, but is hardening his heart to my request. One could also say that I am hardening his heart by repeating my request, even though that is not my intention, since he is becoming more belligerent with each request, If my request becomes a demand, he may think his belligerence is paying off and may continue to ignore my demands. He hears, but is not listening. He sees me and my body language, but he is tuning it out into background noise versus his attention on the game. If I continue checking in and begin threatening sanctions, he may ignore those as well. I am incidentally hardening his heart by my persistent crossing of his will, he is intentionally hardening his heart against my will. He hears but does not listen (the same word in Greek (akuO). He looks but does not take heed (the same word in Greek (blepO). My son has adopyed an attitude that equates to having eyes that do not take heed and ears that do not listen. My insistence on compliance has had the undesirable but perhaps predictable effect of deepening his self-imposed blindness and deafness. When I take his computer away for a few days, he could say, "You made me ignore you by your interrupting me every five minutes. If you had just left me alone, I would have gotten onto it eventually."
I did not intentionally blind and deafen my son, though I could have correctly predicted his response to my interference would be that he would tune out and stop his ears and close his eyes. But the deafness and the blindness was all his own doing. He could have chosen to respond differently.