Strokovnjaki Danske tehnične univerze (Technical University of Denmark, DTU) so decembra 2009 objavili izčrpno študijo o zvoku in hrupu, ki v marsičem obravnava tudi NFH.
Na strani 31 je tudi za osnovno ugotavljanje prisotnosti NFH pomembna ugotovitev, da velike razlika izmerjenih vrednosti s filtrom C in tistimi, izmerjeni s filtrom A, dokazuje prisotnost NFH:
"The sensitivity of the human auditory system varies significantly with the frequency
in a way that changes with the level. In particular the human ear is, at low levels, much less
sensitive to low frequencies than to medium frequencies. This is the background for the standardised
frequency weighting filters shown in figure 1.3.7. The original intention was to
simulate a human ear at various levels, but it has long ago been realised that the human auditory
system is far more complicated than implied by such simple weighting curves, and Band
D-weighting filters are little used today. On the other hand the A-weighted sound pressure
level is the most widely used single-value measure of sound, because the A-weighted
sound pressure level correlates in general much better with the subjective effect of noise than
measurements of the sound pressure level with a flat frequency response. C-weighting, which
is essentially flat in the audible frequency range, is sometimes used in combination with Aweighting,
because a large difference between the A-weighted level and the C-weighted level
is a clear indication of a prominent content of low frequency noise"
Študija FUNDAMENTALS OF ACOUSTICS. AND NOISE CONTROL (december 2009) avtorjev Finn Jacobsen, Torben Poulsen, Jens Holger Rindel,. Anders Christian Gade and Mogens Ohlrich je dosegljiva na naslovu