Figure 15
The figure is arranged in two rows labeled “Left wheel‑rail” on top and “Right wheel‑rail” on the bottom, with each row containing a time‑history plot on the left and a bar spectrum on the right. In both time‑history plots, the horizontal axis is labeled “seconds” and ranges from 265 to 285 with an interval of 5 seconds, while the vertical axis is labeled “Pascals” and ranges from negative 10 to 10 with an interval of 5 in the upper plot and from negative 60 to 40 with an interval of 10 in the lower plot. The left wheel‑rail time trace shows a dense filled waveform centered near 0 Pascals with instantaneous values fluctuating mostly between about negative 4 Pascals and 4 Pascals. The right wheel‑rail time trace is similarly dense but spans a slightly wider band, from roughly negative 25 Pascals to 25 Pascals. In each row’s frequency‑domain panel, the horizontal axis is labeled “Hertz” and appears logarithmic, marked approximately at 10, 100, 1000, and 10000, while the vertical axis on the left is labeled “decibels” and on the right “decibels (A)”, both ranging from 20 to 100 for the top plot and from 20 to 110 for the bottom plot, with gridlines every 10 decibels. In the left wheel‑rail panel, the plotted curve rises from about 39 decibels at 40 hertz to approximately 68 decibels near 200 hertz, then forms a broad plateau between about 76 and 85 decibels from 300 hertz to around 3000 hertz before gradually decreasing toward about 40 decibels by 20000 hertz. In the right wheel‑rail panel, the curve climbs from roughly 35 decibels at 40 hertz to around 83 decibels near 200 hertz, peaks above 95 decibels in the 300 hertz, and then declines slowly to about 63 decibels at 20000 hertz. Note: All the numerical data values are approximated.Time-domain and frequency-domain analysis results of noise from a vehicle speed of 50 km/h-R300 m. Source: Authors’ own work