Noise inside cabin was measured for some planes, but with the use of headsets and their non-linear dampening especially with ANR versions, I guess the numbers are useless. Total noise pressure will tell u'nothing, i.e. 75dbA at low bass frequency from an O300 will not sound like noise, but the same 75dbA from a Rotax 912 sound like dental powerdrill. Which frequency band your personal noise feeling is triggering at is also changing in time, so what for?