> An STC label delineates how partitions and walls effectively block sound and reduce noise. Ratings are determined by broadcasting a specific auditory tone near the material, and measuring dB on both sides. The higher the STC value, the better its insulation.
From the table STC=25 means "Normal speech easily understood" and STC=50 means "Shouting not heard"
This [2] table has one datapoint comparison of "airspace" vs argon filled windows. Both have an STC of 35. So maybe it doesn't help.
[1] https://www.dillmeierglass.com/news/stc-ratings-of-glass
[2] https://www.general-glass.com/wp-content/uploads/2020/09/Aco...