Trefz window prices and experiences?

what should be considered when installing with regard to sound insulation?

A clean installation starts with an accurate measurement, because roughly estimated gap dimensions are the root of many foam disasters. Then it continues with product selection – I prefer MD (middle seal) over AD (stop seal). Cover strips can also be installed more or less carelessly. Ultimately, the panes remain vibration-transmitting membranes, and the resonance frequencies correlate with dimensions – so the sash division also plays a (albeit minor) role. No window can work magic, but from professional experience I can painfully confirm that botched installation gaps allow almost the same amount of noise to flow through, at least subjectively, as if there were no square meters of window area in between at all.

A clean installation starts with an accurate measurement, because roughly estimated gap dimensions are the root of many foam orgies. Then it continues with the product selection – I prefer MD (middle seal) over AD (stop seal). Cover strips can also be installed more or less carelessly. Ultimately, the panes remain vibration-transmitting membranes, and the resonance frequencies correlate with dimensions – so the sash division also plays a role (albeit a small one). No window can work magic, but from professional experience I can painfully confirm that botched installation gaps at least feel like almost the same amount of noise flows through as if the square meters of window surface weren’t there at all.

Then why don’t I hear the noises through the window frame or wall connection? It is clearly detectable with the ear that the panes vibrate at low frequencies and offer no sound insulation at all. Maybe you can explain that to me, these are modern triple-glazed insulating windows. They filter out high tones well, but every car or plane below 6000 m altitude is heard inside with a loud low-frequency rumble. Very disturbing!

If you cannot hear anything through the wall connection, it means that it was executed properly. The "triple insulating" glazing refers to heat transfer, not sound transmission. From a sound perspective, there is no triple glazing; the entire thickness of the glass without an air gap would be a greater barrier to sound. Sound wants to pass through (or release its energy to a membrane, such as the pane). The pane is not suitable as a tweeter / high-frequency transmitter - naturally, it shifts the frequency spectrum towards "low." In the space between the panes, the vibration cannot be damped out; for that, a flexible suspension of the middle pane would be needed.