Article,
A-weighted sound pressure level as a loudness/annoyance indicator for environmental sounds – Could it be improved?
Applied Acoustics, (2007)
Abstract
A system is introduced with the purpose of showing how an auditory
perception system may be built up to include the basic quantities
on loudness domain. The quantities are the critical bands, the power
law, and the weighting. The power law seems to be the most crucial
basis for hypothesizing a loudness function. It has been shown that
the power law could be applied as such by assuming the auditory perception
system to have two essentially different stimuli: the intensity (sound
pressure level) and pure pressure. These physically different quantities
seem to be combined in the root of the power law, and in this study
the roots are determined from equal-loudness contours. A loudness
function is derived on the basis of this finding. By adding the weighting,
a method has been constructed for assessing loudness. After defining
the weighting, the equal-loudness contours are constructed and are
seen to be virtually identical to the contours in ISO 226. It has
also been found that the equations for deriving the contours in this
standard and in the new ISO 226 may be incorrect, because there is
no definition of a sensible loudness function. Finally, it is deduced
that the derived weighting must be unequivocal for an auditory perception
system (depending solely on the otologically representative group).
Finally, the A-weighting (as part of an A-weighted sound pressure
level) as such is reasonably similar to the weighting derived in
this study. Therefore, this weighting is not the main problem when
assessing sounds in respect to loudness. The A-weighting is thus
chosen as the weighting for the indicator derived in the study for
assessing environmental sounds.
