Why do humming sounds stop when we plug our nose?

Why does the humming sound stop when we plug our nose while humming sound

Any vocal sound, weather it is speaking, singing or humming, is created by air passing through our vocal cords, a pair of membranes located in the voice box in the throat. The vocal cords cannot be activated unless there is air passing through them. When the air passes through vocal cords, they vibrate and produce sound. The mouth simply provides articulation to this sound as the air passes through it. While humming, the mouth is closed and the nose is the only way left for the air to escape. We we plug our nose, the vocal cords cannot vibrate. Hence, humming stops.