Same problem here. It started with Parallels 8. I thought that it would be sorted out with 9 but not. The sound comes from the speakers on my MacBookPro even though everything is muted. Every time I open a window in windows 7 (which haven't change since Parallels 6) the 'knocking' sound comes twice as stated above. It looks like it sounds when the open window process starts and sounds again when the window is stabilized.
Would it be a new driver for the sound hardware that is causing it?
PS.: I'm adding this after posting.
I'm not sure if it is Parallels related issue or an OS issue. By the time I started having the 'knocking' I have updated from OSX 10.7 to 10.8. However I do not have that 'knocking' with any other app besides Parallels and only when the guest is windows 7. I have Ubuntu guest and all is fine there.
Second post editing:
I have disabled the Parallels Audio Controller in Control Panel -> Sounds and the 'knocking' is gone. I have rebooted my MBP and started Parallels as this is a confirmed way of reproducing the 'knocking' and nothing up to now!
Third post editing:
I have several Windows 7 VM. some 32bit other 64 bit. Interestingly, after disable the Audio Controller in one VM, I cannot anymore reproduce the 'knocking' in the other VMs, even though they have the Audio Controller activated and are able to reproduce sounds and music. It seems that the deactivation of the Audio Controller in the VM have, some how, impact in Parallels Desktop.
Forth post editing: (this is getting long..
I have just received and installed a Parallels update. It is build 9.0.24172 Rev.951362. The Audio controller is activated and I'm not able to reproduce any 'knocking' so far. It seems sorted out. Can anybody confirm this?
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