C de L! How the heck are you?
Can you give a little more detail? How loud is it? Does it do it all the time? just after flushing? can you tell where it's coming from? louder with the tank lid off? Have you called Toto?
Monica

Hi Monica! I'm a little crazed. Well...it's pretty loud. It does it all the time, and flushing doesn't seem to make any difference. I don't know where it's coming from exactly except I know it's from the toilet, and NO I haven't called Toto yet. I guess I will try e-mailing them first, but I thought I'd ask here.

I don't know if it's connected to the Washlet or not...I can't really tell. Oh brother. Am I the first to report this as a problem?

Have you tried unplugging the Washlet to see if the humming stopped? Could it be coming from the water line? Have you tried turning off the water? Is it a mechanical humm? Can you tell I'm not a plumber? (g) My Toto made a noise for awhile but it wasn't a humm. I recorded the noise with my camera and emailed it to Toto tech support. They sent a part, David replaced it and all is well. Good luck!
Monica

No, I haven't done any of those things. We are at the ''What IS that?'' stage, but haven't actually investigated anything yet. Thank you Monica, those are all good places to start, and start is what I will do. Since it hasn't posed any physical problems yet, it hasn't been important enough to do anything about it except complain to each other. I'll let you know what we discover, when discovery is made!

I have a humming noise in mine only after someone has sat down and flushed and it lasts for a long 30 minutes. It drives me crazy. Is this normal?

water fill noise can make a reverberating sound, but that usually occurs during the flush/fill cycle.

If it's continuing after the water flow has stopped, it may be the fan. There's usually a way to turn the fan off through the setting menu.

Most practical way would be to turn the features off one at a time. Fan, seat heater, water heater, etc. That may help isolate.

Some washlets have an over-sensitive sensor. As soon as the door is open, it starts a heating/fan cycle, etc. I know a few folk who have disabled or reduced it's sensitivity with tape.

I was able to track the buzz down to the filter at the rear of the unit - removed cover, reseated filter, and buzz is gone. The filter was vibrating in its seat causing the annoying noise.

What is the filter at the rear? Mine is getting really loud too

I have this buzz/hum as well with a 2.5 year old Toto washlet. Toto said I should take the seat in for service. What are we to do? Buy a spare seat for who knows how long?