MY wife does this all the time, I don't know how many times I've said to her "can you not hear that sound?" for her to respond with "What sound???". It really gets my goat, especially with her car, I checked the front disks and pads a couple of months ago told her to get them changed (she wont let me do it... another story that one) low and behold when I drove her car 1 week ago the breaks were metal on metal..... GGRRRRRRR two days later I got the mechanic to replace them..