Interior walls: aerated concrete, sand-lime brick, or lightweight walls?

Hello,

before you write: Yes, I know, the question comes up often enough, and there are similar questions here and on the web, but somehow every case is individual.
Regarding our single-family house new-build project, I have the following question about the interior walls:

-The structural engineer recommends calcium silicate brick due to better sound insulation, but he can also manage the statics with interior walls without any problem.
-The mason recommends aerated concrete because it harmoniously integrates with the aerated concrete exterior walls as well as the floor slab, ceiling, ring beam, columns,... With interior walls made of calcium silicate brick, there is a risk of cracking due to mixed masonry. In addition, he can certainly handle aerated concrete more easily.
-I am torn: On the one hand, I tend to leave the mason to his familiar work method and material since the craftsman best builds what he usually builds. On the other hand, I worry about the sound insulation between the bedrooms. Our two girls play music (piano and clarinet), and the children (7, 10, and 12 years old) are growing and might make more noise over time (puberty
Or can I take lightweight partition walls as a compromise between the bedrooms on the upper floor? Are these better regarding sound insulation, and what does their construction look like?

What would you suggest? Please also from personal experience!

On the one hand, I tend to let the mason stick to his usual working method and materials, since the craftsman builds best what he usually builds.

I basically consider that reasonable, but I actually see no conflict there:

The mason recommends aerated concrete because it harmoniously integrates with the aerated concrete exterior walls as well as the base slab, ceiling, ring beam, columns, etc. With interior walls made of calcium silicate brick, there is a risk of cracking because of the mixed masonry. Besides, he can certainly work with aerated concrete more easily.

That is also basically a correct way of thinking. However, the calcium silicate interior walls do not have to align anywhere, as they may be butted flush. So the mason builds the exterior walls regardless of the interior walls and creates the calcium silicate interior walls in a later separate step. There is not much to work on those here, since the affected walls have uncomplicated layouts without tricky connections. Plaster in corners where two different wall materials meet can be reinforced. That if the sun fell into the sea every evening, the earth would have to be flat, sounded logical for centuries. The popular belief that the heavier stone obstructs sound better follows the same line of thought. I personally would do both without concern: placing calcium silicate interior walls between exterior walls made of other stones just as in a homogeneous aerated concrete house poses no fear of sound. By the way, calcium silicate bricks are now also available as plan bricks (and in 11.5 cm thickness also in large formats), so the mason hardly has to rethink processing between exterior wall material and interior wall material. In the case of Ytong / Silka, aerated concrete and calcium silicate are even supplied by one source. But other stone manufacturers are also experienced in the proper combination due to the general popularity of calcium silicate interior walls regardless of the exterior masonry used.

Yes, I know, the question comes up often enough, and there are similar questions here

And quite recently:

Thank you 11ant for your detailed answer. Overall, it makes - in your eyes - no significant difference, if I have understood correctly?

Yes, both acoustically and in terms of construction. Of the three alternatives, combining an aerated concrete exterior wall with an interior wall also made of aerated concrete or made of KS or lightweight construction, there is no catastrophe and no panacea among them.

By the way, acoustic construction is not only about interior walls. What I would be more concerned about in your place – I interpret the well-known floor plan as no change in this regard – is the heat accumulation pressing against the head end in the bedroom from the conservatory (as I already mentioned).