Anyone who owns an AQT 3001 aquarium filter...?

I've opened up the pump and I didn't notice anything that would store the bubbles, cause it to stall or pump out at any intervals Test it. Take off the hose and feel if the air is pumping consistently then it should be working fine. If there is a problem and there isn't air coming out you should have it fixed or replaced.

I wish I could have more information about your set up, but what I think is going on is that you have an under-gravel filter and you put the air stone, all the way under the grating, so what is going on is that the tiny bubbles are forming and coming together and when they finally find a way out from where they are hiding a big bubble comes up from the opening which is causing that sound. You should have the air hose connected to the stone positioned inside the tube that goes up about 2 inches from the bottom so that in water will flow upward and outward along with the tiny bubbles and create a vacuum to suck the water through the gravel. This will become your biological filter where the good bacteria that break down the nitrates will live so your tanks water stays clear.