I would carefully go over the ozone hose from the ozone generator to the injector, looking for cracks or holes.
If you have the soft, flexible black tubing, it may have failed. If so, it will suck in additional air, and that can contribute to the noise you are hearing.
If so, just go to your dealer. They should know about it - if not, ask them to call the tech hotline and find out.
If it is easier/quicker, or you just want to do it yourself, go to the home center and buy some tube. I use standard vinyl tubing to replace it with. It has given us better service than you would expect: some have been running with it now for five years. It turns brown inside, but it seems to stay in place and do the job. You may need to put the ends in a cup of hot water to get them to ease onto the barbed fittings and the check valve.
If your tubing is good from end to end, call your dealer. I had some little valves sent to me to install on a noisy ozone. They were simply aquarium brass valves with short lengths of tubing in place to make them slip in easily. You turn the valve down until you still get bubles but no noise. Works like a charm.
