Application of land-use regression models to estimate sound pressure levels and frequency components of road traffic noise in Taichung, Taiwan

Few studies have applied land-use regression to predict road traffic noise exposure, and there are few predictive models for different frequencies. This study aimed to measure 24-h average road traffic noise levels and to analyze the frequency components over one year to establish land-use regression models of noise exposure. Fifty monitoring stations were set up to conduct 3 measurements for A-weighted equivalent sound pressure levels over 24 h (L-eq,L-24h) and night equivalent sound pressure levels (L-night), as well as octave-band analyses, during the 2013-2014 period. Noise measurements were integrated with land-use types, road and traffic information, meteorological data and geographic information systems to construct land-use regression models. Leave-one-out cross-validation was performed to test the validity of the predictive models. The annual means of L-eq,L-24h and L-night were 66.4 +/- 4.7 A-weighed decibels (dBA) and 62.1 +/- 6.0 dBA, respectively. Octave-band frequency analyses revealed that the highest means over 24 h and at night were 61.4 +/- 5.3 decibels (dB) and 56.7 +/- 6.6 dB (both at 1000 Hz), respectively. The model-explained variance (R-2) of the full-frequency noise was 0.83 for L-eq,L-24h and 0.79 for L-night. The R-2 values for octave-band-frequency noise ranged from 0.67 to 0.88 for L-eq,L-24h and 0.65 to 0.85 for L-night, with the highest R-2 at 250 Hz for L-eq,L-24h and at 125 Hz for L-night. The differences between the model R-2 and the leave-one-out cross-validation R-2 ranged from 5% to 15% for both L-eq,L-24h and L-night at all frequencies. In the validation, the root mean squared error was 2.09 dBA and 2.80 dBA for the full-frequency L-eq,L-24 and L-night, respectively, and ranged from 1.89 to 2.62 dB and from 2.51 to 3.28 dB for the octave-band-frequency L-eq,L-24h and L-night, respectively. This study observed that the annual means of the measured L-eq,L-24h and L-night in Taichung were both above 60 dBA and had the highest level at 1000 Hz. The developed land-use regression models of L-eq,L-24 and L-night both had good predictive capacity for the full frequency spectrum and within octave bands and can therefore be applied for epidemiological studies.