Stud Wall Question

[robg8950]

I am going to be wall mounting my tv in my flat. the walls are all stud.
I have done the knock on the wall and marked with a pen.

The timbers are 60cm apart with hollow in between.

but then when you knock vertically up and down the timbers they also go hard and then hollow.

so therefor i seem to have hard squares that are 40cm apart vertically on each stud

Example image attached. Im a tad confused.

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[mfarrow]

There are noggins/dwangs between the studs for added rigidity. Nothing to worry about, but might make a good mounting point for the TV.

 

[robg8950]

So as i tap up and down it goes holow then hard is nothing to be worried about.

 

[mfarrow]

Yes, nothing to worry about.