Thanks FurryNutz!
The router is a Netgear VMDG485 (Super Hub 2), using 2.4GHz/5GHz SSID.
I've tried the camera in a few different rooms ranging from 1 - 10m from the router and the static noise is consistent.
There are Panasonic KX-TG8561E phones in the house (1.88 - 1.90 GHz), but I unplugged them all and it didn't make any difference - noise level stayed 40 - 60DB according to the mydlink app.
There are no WiFi access points in our house, though we do live in an urban residential area.
I couldn't see a way to get 'Network Analyzer Lite' to list nearby routers, but if I browse my laptop there are 15 other WiFi networks within range.
Within our home network we have laptops, tablets and smartphones. Also two Sonos boxes. No unusual electronics for a standard residential property.
I can't confirm if the issue was present prior to the firmware change as it prompted me to upgrade upon initial configuration.
Any thoughts?