This figure shows a comparison of the SiO spectra extracted from regions with low signal-to-noise and non-detected SiO emission. Black curves represent the SiO spectra extracted from positions 2, 9, 10, 11, 12, and 17. The purple curves show the SiO spectra extracted from the purple circular regions with no SiO emission, as indicated in Figure 2. The numbers at the upper-right corner of each panel correspond to the labels of these circular regions. The purple dashed parallel lines indicate the 3σ noise levels of the SiO emission from non-emission regions. The vertical dashed-dotted black line marks the central velocity of Cloud H (45.5 km ⁻¹).