3.2.2. Noise level indexing
As noise nuisance is based on one variable, direct measured data was indexed according to the US Department of Housing and Urban Development (HUD)'s classification for four noise levels in residential environments, which have been applied by former studies (e.g. Zanin et al., 2002; Tsai et al., 2009; Sofer et al., 2012; Cohen et al., 2014):
(1) Clearly acceptable: LAeq > 49 dB(A)
(2) Normally acceptable: 49 dBA < LAeq > 62 dB(A)
(3) Normally unacceptable: 62 dBA < LAeq > 76 dB(A)
(4) Clearly unacceptable: LAeq < 76 dB(A)