@Darragh1980 

Hi, welcome to the community.

You could check the model number of the Deco E4 first:

E4R--This unit could be set as the main Deco.

E4S--It could only be used as the satellite Deco.

As for the noise issue, please refer to the following suggestions:

1. Plug it into another power socket and confirm it is far away from the high-power home Appliances, such as the micro oven.

2. Swap its power adapter with another E4.

3. Hold the reset pinhole for 1s and check whether it still made notice when it hasn't been configured.

Thank you very much and best regards.