I have had this unit for 3 months. When plugged into the wall outlet, the unit has a 60hz hum along with the selected sound...irritating!I typically use it as a portable unit on batteries. However, because of the 2 LED lights that shine brightly and disturb my trying to get to sleep, (I have a serious case of "screaming" tinnitus) the battery runs down fast.The design is bad. It should have 4 timer buttons (stop, 30 min, 60 min and continuous, each would turn on the sound for a designated time with no lights except for continuous when the unit is probably plugged in.