It sounds like that noise what comes from fridge sometimes... I wouldn't say that it is LOUD but I can hear it ALL THE TIME ???? I can't mask it with anything!! I hope it is just a spike because I have stress and I smoked yesterday like 3 cigarettes... Could it be just a spike? I have never experienced anything like this and this drives me totally crazy!!! I'm now in the car and still I hear low humming/ringing... aaargh!!