Page 72 - Studia Universitatis Hereditati, vol 12(2) (2024)

Table 1. Environmental Sound Propagation Factors that are Included in the SPreAD-GIS Calculation Process
Environmental sound propagation factors Declining the sound level due to…
Spherical Spreading Loss Distance
Atmospheric Absorption Loss Atmospheric absorption which depends on temperature, humid-
ity and elevation
Foliage and Ground Cover Loss Absorption by the ground and scattering by vegetation
Downwind and Upwind Loss Wind direction, wind speed, seasonal conditions
Terrain Effects Barrier effects from hills or ridgelines
Predicted Noise Propagation The difference between introduced and background levels

barren land, coniferous forest, herbaceous/grass- validation allowed us to proceed with further
72 land, deciduous forest, scrubland, urban/devel- testing under different weather conditions.
oped land, and water. DEM and NLCD were set Anticipating that the simulations would
studia universitatis hereditati, letnik 12 (2024), številka 2 / volume 12 (2024), number 2
at the same resolution of 10x10 meters, the high- reveal the extremes of sound propagation un-
est available resolution for the NLCD in this der different weather conditions, we conducted
Catalan region. We also introduced data relat- simulations for both extreme winter and sum-
ed to the sound source, including the location of mer days (B and C, tab. 4). Meteorological data
the Àneu bell and a frequency table with meas- were sourced from Servei Meteorològic de Cata-
ured sound levels in the one-third octave fre- lunya (n.d.), including data from nearby stations.
quency bands from 400–2000 Hz, recorded at Wind data were obtained from Tírvia, extreme
a distance of 11 m (tab. 2). temperature data from the last 50 years were tak-
To validate the simulation, we first recre- en from Tremp, and humidity data were collect-
ated the weather conditions present during the ed from La Pobla de Segur. Given that wind sig-
field measurements (tab. 4, weather scenario nificantly influences sound propagation, we also
A.1). Then, we generated the sound propagation tested conditions with the most favorable wind
map, showing sound levels at the receiver points direction, blowing from SSE towards Esterri
(fig. 5). Tab. 3 compares the measured and sim- d’Àneu (tab. 4, A.2.).
ulated sound levels, showing a deviation of 3 to
4 dBA, an acceptable range for validation. This

Table 2. The Frequency Table Used to Characterize the Sound Source for the SPreAD-GIS Simulation,
Including Sound Pressure Levels (dBA) in the One-third Octave Frequency Bands from 400–2000 Hz,
Recorded at 11 m from the Source.

Frequency (Hz) 400 500 630 800 1000 1250 1600 2000
Sound Pressure Level (dBA) 47 73 69 70 81 80 76 80
Table 3. Measured vs. Simulated Values of Sound Pressure Levels for Two Receiver Points on the Site of Santa Maria
d’Àneu
Measured values (L AF; dBA) Simulated val-
Receiver ID Receiver location
1st toll 2nd toll 3rd toll ues (dBA)
1 In front of the church and bell gable 81.7 80.3 90.7 85
2 On the earthen road behind the church 60.2 53.3 56.2 64