opening drivers door

[old cruiser]

Only just noticed the car doing this; unlock car with remote then only when I open the drivers door I get think sort of light clunk noise that appears to come from the back of the car, is this somehow related to the boot mechanism does anyone know?
Cheers Pete

 

[Pacman8184]

Is this not the little flaps at the back of the car for air circulation? And when you open the door it caused a bit of a vacuum and makes the flaps on this vent move. Making the noise? I had this on my civic. Sounds the same to me.

 

[old cruiser]

That's an interesting one mate with the flaps, didn't know it had these, I don't remember this happening on my last car which was also a 2004 civic, do you know where the flaps are actually located?
Cheers Pete