Dump the 22 and get a 24 and you'll have no sound issues.
I can't imagine a more misleading or less helpful statement. That implies that it is particular models that have noise issues, when as has been pointed out, all models have the two things that can get noisy, which are the HDD and the cooling fan, and there is no correlation between either of those and model numbers, at least certainly not strict correlation.
I have seen this complaint regarding probably every model available, including the HR20 and the HR21, of which I have had 8 different versions of with absolutely never a noise problem.
The only conclusion to be drawn is that if a model develops noise, that it is likely that the HDD or the fan is on borrowed time, and there really is only one way to solve that problem, short of adding an external drive (which will neither solve the noise problem nor determine the cause).
Call it in, get it replaced. Try to watch what you can and not record if possible; move what you can to a 16x9 DVDR if you like. Move on.