Shutter sound vs Aperture ! Sony a77

Hello,

after using the Sony SLT-a77 for 5 months something weird happened.

as I go up with F-number the shutter sound changes ,I hear a noisy click with the shutter sound !

I'm really wondering what is the relationship between aperture and shutter sound ! 

I tried 3 lenses (Sony 16-50mm 2.8 , Sony 50mm 1.4 and Sigma 70-300mm 4.0-5.6) all having the same problem.

plus ,photos are getting more noise as I close the aperture !

noticeable noise (will try to post some photos later)

I just want to know if anyone had the same problem ,i made a video for this issue

http://www.youtube.com/watch?v=6ja5G9gIvPc&feature=youtu.be

I hope that the sound is clear