About the word "edge"!!

Hey,guys.

I am really feeling at lost for the meaning of word "edge" in the sentences like:

"But it's cold," I complained. It surprised me when he chuckled under his breath.

There was an edge to the sound. (The Twilight Saga:Twilight, P58)





"Yes — giving up trying to be good. I'm just going to do what I want now, and let the chips

fall where they may." His smile faded as he explained, and a hard edge crept into his voice.

(The Twilight Saga:Twilight, P88)



He laughed, and there was an edge to his laughter. (The Twilight Saga:Twilight, P108)

His voice had a hard edge. "You're driving it home."(The Twilight Saga:Twilight, P386)



I have checked it up in the dictionary,which say "edge" means "a slight but noticable sharpness and keeness",but some other dictionaries says it is" a quality in someone's voice that makes it sound slightly angry or impatient."

So i got quite confused,how do you understand these sentences.

Thankssssssssssss!