For any strange noises, including, mechanical, grinding, whirring, or beeping sounds, please perform the following steps. 

• Unplug the unit from the wall
• Remove the panel and the filter from the unit
• Let the unit sit for a few seconds without the filter or panel installed
• Reinstall the filter, making sure that it is placed securely back in the unit
• Put the panel back on the unit
• Plug the unit back into the wall
• Power on the unit