Answer:
• Hum with your mouth and nose open:
I could hum and feel vibrations in my throat.
• Hum with your mouth open and nose closed:
I tried to hum but nothing came out
• Hum with your mouth closed and nose open:
I could still hum and make noise
• Hum with your mouth and nose closed:
I tried to hum but I couldn't
Hope this helps and have a great day! =D