There is no db model number. Just make sure that You are buying:
Yokohama dB Decible (E-Spec) in required SIZE
Check the date of manufacturing. It should be either 2011 made of LATE 2010 made. LATE means November/December.
Plus there is no such thing as WARRANTY of a tire. Its just their publicity stunt. If you tire gets deshaped for no reason then they will NEVER entertain your claim for free replacement by stating that it has deshaped due to low air pressure or by hitting somewhere. So donnot fall for this warranty thing. And if he is giving you warranty for 2-3 years then its fine altough it means nothing but still after 2-3 years you'll have to replace your tires.
Life time warranty=Means nothing= Until you marry those tires.