Four years ago I went looking for a quiet sewing machine. I took a sound level meter with me and used it as I tried out various machines at different stores. I kept records in a notebook and found that Janome was the quietest. I admit that the sales clerks were amused, saying no one had ever done that.
I didn't buy a Janome, as I fell for a Pfaff, but at that time, it was the quietest. I don't know what model or anything, but if you are interested in that sound level meter, which I know not everyone has...this was my husband's...he told me that folks who are heavy into stereo music might have one, or they are available at Radio Shack for $39.
I found quite a variety of noise levels in the machines I tried. All were quieter than the machine I had been using.
Hope this is helpful...
Dina