As a caveat, learn to listen under water. Everyone breathes a bit differently, even your instructor. So listen to them intently and figure out what makes their breathing unique. If you can't hear them, then you're too far away. I know the text books teach that you can't figure out direction under water because sound travels so much faster and I disagree. With a bit on concentration, it's just not that hard. If I can hear you, I can find you. Sometimes it helps to close my eyes. It's the one drawback to diving on rebreathers.
BTW, don't expect to figure this out on the first try.