I have owned several cab tractors and gave db checked them all.
2005 kubota l3430hstc =84db
2008 kubota l3240hstc =77db
2006 john deere 3320 cab =77db
I bought my L3240 cab new in 2008. When it was new it had very noticable hydro whine and it was always louder under a load. This is completely normal. I have found out that part of the whine is due to it needing to be broke in. At aprox 700hrs its just about completely gone, very little whine to speak of. The cab is very quiet and no need for any ear protection at all. I have almost 3000 hours on my 3240 now and it still runs like new! No oil use no oil leaks no trans problems and a/c still cold!
Cabs are worth every penny you pay. I hit a underground bumblebee nest yesterday bushoging and i was covered in bees trying to get in my cab!! I also hit a underground hornet nest a few years back!!