A single phase Symmetra UPS system will generate audible noise that is no greater than 62 dba.  The majority of this noise is generated by the power modules.  The power modules can sometimes emit a buzz or hum noise that is more audible than the noise other power modules of the same type.

Symmetra LX

Symmetra RM

Symmetra Power Array

All manufactured systems in the above product lines

The difference in audible noise is caused by power modules emitting noise at varying frequencies which create a buzzing or humming noise.  This can become especially apparent when installing new power modules or comparing the noise between two different Symmetra LX systems.

The inverters in the power modules will emit a buzz or hum noise during online and on battery operation.  It is typical that this noise will vary slightly from module to module, i.e. some modules may present a more audible noise than others.

This buzzing sound emitting from the Power Module is normal operation of the system and does not represent a problem.  Symmetra modules are designed to instantaneously detect and act on any abnormal conditions within the module and disconnect themselves from the output if there is a problem.  If the system is not showing any power module faults, there is no cause for concern.  To ensure the system is running normally, a self-test can be done by the user via the PowerView display or network management card.