Lee and Gertie are right: "the sound made by my mom when she cooks" and "the sound of my mom cooking" both work, but "the sound of my mom cooking" sounds more natural. Where I live (Arkansas, in the U.S.), "the sound of my mom cooking" is a bit formal. I would say it like that if I were writing an essay, but if I'm talking with friends I would say "the sounds my mom makes when she's cooking."

I agree with your friends. And Lee when he said to use "are there" instead of "were there".

Grammatically, those are both correct ways to express the same idea. However, in your question, you should say "Are there," not "Were there."