Drive acoustics WD5000AADS

I’m very interested in the data on WD5000AADS, but there is a big difference in acoustics reported, PDF file:
states 21, 22 and 22 for the 500 GB drive… but the page:
states 25, 29 and 26 for the same drive…
What are the correct figures on the acoustics for WD5000AADS?

Another question on this drive, how many platters does it have?

 Response (Jose N.) 03/31/2010 04:16 AM
Dear Bengt,

Thank you for contacting Western Digital Customer Service and Support. My name is Jose N.

It depends on the firmware, last link is the one we have on sale.

but the page:
states 25, 29 and 26 dB for the same drive...

I hope that we have met your expectations today and that you are satisfied with our service. If you have any further questions, please reply to this email and we will be happy to assist you further.

Jose N.
Western Digital Service and Support

Thank you for the response/Bengt