How to clean and lubricate gearing for casement windows

Single glazing with storm windows absorbs sound reasonably well, I would not expect a huge decrease in sound level with triple glazing, but certainly not an increase. Single glazing alone is another story, it's sound absorption is terrible.

The increased sound is certainly due to the frames and adjacent construction. While there is often a correlation between thermal loss and sound transmission, sound is much trickier to manage well. It is sometimes counter intuitive. The construction joints must be carefully detailed. The general concept is to avoid any solid connection between inner and outer surfaces. Any connections should be via resilient, absorbent materials. Typically, you want to fill any voids with sound insulation, though in some cases this has been worse than a simple air gap.

Also consider exterior sound attenuators. Walls, fences, trellises, large shrubs, trees, berms all will help attenuate sound, but when you consider cost vs. benefits, such measures need to be carefully considered.

Quality sliding PVC windows use rollers. Keep the tracks clean, using a slightly damp lint-free cloth. The rollers take care of themselves.

On cheap PVC sliders, I use paste wax after cleaning the slot with a slightly damp lint-free cloth.

You can also use spray silicone. Clean the track with a slightly damp lint-free cloth. Spray the silicone on another lint-free cloth and wipe the track down.

Don't use any petroleum lubricants on PVC if you want it to last.