UPS converts power and the conversion always generate heat. Converting more power generates more heat. Such heat needs to remove from the UPS to keep it cool and operate normally. For small power UPS, the heat could be dispersed by nature air flow. For larger UPS, such as 1000VA or above, most of them need fans when converting. For online UPS, its double conversion feature works always. To make sure the system can operate smoothly, the fans are forced to turn to disperse the heat. Even with smart control, the fans speed varies according to the power. However, it still generates certain level audible noise even in low power mode. Thus, online UPS is not installed at the rooms where special quiet environment is required, such as bedroom, studio, reading room and study room.
For such application at the place where low noise is required, people use the following workarounds:

    1. Installing the UPS outside the room, then connect power lines from the UPS outlet to the place inside the room. If the UPS is installed close to power distribution panel, you might not need extra power lines
    2. Putting the UPS in a closet with acoustic foam inside. It needs to be careful for this workaround to keep the space for air flow of the fans. Besides, with this, the UPS temperature will increase a little (around 1 to 2 degrees), the benefit is to gain around 8 to 10 dB lower noise