Humming noise Camberwell Grove / DKH area

[Rokit2022]

There is an intermittent deep sound hum noise (last a few seconds) every 10 minutes or so, in the Camberwell Grove / Grove Hill / DKH area.  Audible at night.

Does anyone know where it is coming from, or what’s causing it? Thought it might be rail works but its regularity seems unlikely.

 

[Penguin68]

Is there an electricity sub station anywhere in the vicinity? 

 

[Rokit2022]

No - hence the question as to where it’s coming from.