It could be worth the ask as to whether the current owners were the ones who had it installed - it may have been something installed 10 years ago by a previous owner to deal with a neighbour playing DnB until midnight who has long since moved on and is absolutely nothing to worry about.
Edit - that last photo is ground floor, the original photo you posted was first floor
The ground floor doesn't look to have as much 'sound insulation'
Edit - that last photo is ground floor, the original photo you posted was first floor
The ground floor doesn't look to have as much 'sound insulation'