Recently I have had this ... noise, in my ears. It's like white noise and sometimes I can hear like, popping kinda noises. I researched it and it said something about Clairaudience... everything has been alot louder lately and i've realized that if I really concentrate I can hear distant things like a car door being opened or people talking down the road, sometimes I even hear my name but no one called me. Yesterday I heard mumbling which was really frustrating because I was trying to understand it but I just couldn't. Also, whenever I try to concentrate really hard on listening, I feel drained...
Honestly I have never heard of this before, but it seems to make sense. Similiar to clarivoyance and clairsentience, instead you're picking up on sounds and sound waves. Your ears have become sensitive to sounds that it feels you need to hear, as well as those that are existing around you on the spirit plane.
My guess is, since this is a new skill you've developed, you're feeling drained because you're out of practice. Working on maintaining the connection by starting for short periods of time and then slowly increasing them will help you to strengthen your ability.
I'm actually clairaudient as well. It works differently for different people, but there are various exercises that you can do to get used to it. The following one is pulled from "The Element Encyclopedia of Ghosts and Hauntings"-- a fantastic reference for information on virtually anything occult-based, by the way. In particular, it's from page 86.
"Find a place where you feel comfortable and won't be disturbed. Sit down, relax, and breathe deeply. Imagine a shield of golden light around your ears for hearing and protection. Next, imagine a tuning knob such as one a radio in front of you. With this knob you can tune your hearing to a new frequency-- that of your higher awareness-- where you can receive clairaudiant guidance. Sense a subtle sound change as you adjust the frequency. Note whatever information you receive. You may receive very little at first, but keep trying, and after a while you might find that your ears automatically tune to receive clairaudiant information whenever you focus."
Keep in mind that this may not work right away or at all, but it's the one I used for a while before I got to the point I'm at. This particular book has a great definition for claidaudience too, but it's a bit lengthy to type out. Also, the mumbling you heard could very well be a spirit guide; sometimes they can sound a bit garbled until you practice listening to them.
I hope this is helpful. Feel free to message me with any questions or anything.