Mysterious knocking noise from roof...except when tv is on!

[Tombochan]

Hello,

I wonder if anybody knows what this is. I live on the top floor of a block that's 3 years old. A few days ago, a mysterious knocking sound started coming from the roof, near the balcony end. We have a flat roof. It is literally as if someone was up on the roof and was hitting it with their knuckles a few times every minute. It continues all day and all night, even when there is no wind.

The puzzling part is, that we discovered if we put the tv on - even if muted - the noise disappears. ????

Does anyone have any idea what this may be? And please don't say it's a ghost with a TV addiction!

Thanks.

 

[datarebal]

Leave the TV on

 

[leezer3]

Communal TV amplifier is up the creak IMHO.
Probably an electrical issue within it somewhere which vanishes when a load is put on (Your TV). Try it with a neighbours, and if this is the problem, the knocking ought to vanish.