Aural Nondetectability limits
Aural Nondetectability limits
(OP)
Can anyone explain the aural nondetectability section of Mil Std 147C.
From table IV the aural nondetectability at 2500Hz at 20m is 28dB and at 30m is 23dB, the AD decreases with distance, while most of the table shows the AD increasing with distance.
Thanks
From table IV the aural nondetectability at 2500Hz at 20m is 28dB and at 30m is 23dB, the AD decreases with distance, while most of the table shows the AD increasing with distance.
Thanks





RE: Aural Nondetectability limits
I can only guess that the tables are based on actual measurements and that they either changed microphones or amplifiers at those ranges, or the data was simply too noisy and they picked some osrt of envelope as the spec limit. This is partly borne out in the graphs for non-detectability
TTFN
RE: Aural Nondetectability limits
The boss of the first NVH group I ever worked in had spent a couple of years measuring this stuff for the military - if there were no surprises I guess it would have taken a month!
Cheers
Greg Locock