ᐅ Drywall cavities without insulation? What is the sound insulation value?

Hello,
we plan to install new drywall partitions. All will be between heated rooms, drywall sheets on metal studs. For weight and cost reasons, we would prefer to skip insulation material between the drywall sheets. However, we want to double-layer the wall with 12.5 mm (1/2 inch) boards. Does anyone have experience with this kind of construction without insulation? Does anyone perhaps even know the respective sound insulation values (double-layered 12.5 mm drywall without insulation versus with insulation)?
Sound transmission depends on many factors. We assume proper installation and mounting of the walls. But one question for us is: Doesn’t sound mostly travel through, for example, the doors (if they are not specially insulated), while the wall itself has good insulation but the sound finds its way through the door?
Experience-based or theoretical values would be really helpful.
Thanks in advance and best regards

Sound is air pressure that naturally seeks to equalize. Its direction of propagation (when it can move freely without different resistances interfering) varies depending on the frequency. Try searching for bass reflex speakers and compound speakers to find the principles you are basically replicating with the lightweight wall. Without insulation in between, you can expect significantly better transmission efficiency for exactly the frequency range of the noises produced by everyday living. I would recommend at least horizontal timber battens at mid-height to dampen the vibrations of the panels.

The sound level rating "dB(A)" is intended to mimic human hearing, but I would not consider the psychoacoustic accuracy to be perfectly reflected in the measured values. Once you understand the underlying principles, you don’t rely so rigidly on the numerical values.

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Search for "Knauf W11" online. You’ll find a lot of useful information about gypsum board partition walls. However, you won’t find sound insulation values without mineral wool, as that is simply no longer considered state-of-the-art. Without mineral wool, the sound reduction drops by a few decibels.

It is important to keep in mind that these values are somewhat lower nowadays compared to a few years ago because the density of gypsum boards has been reduced. That’s why there are specialized acoustic studs and/or diamond boards available for better sound insulation performance.

I have a double-layer gypsum board wall with 40mm (1.6 inches) of mineral wool between the kitchen and the bedroom. Even this wall is more sound-transmissive than some masonry walls but still acceptable. I definitely wouldn’t want this wall without mineral wool!

Forget about going without insulation. You might as well just hang a curtain—it would have the same effect.
I would recommend not to skimp on insulation. If the renovation gets delayed, so be it.
Use double drywall layers on both sides and 60mm (2.4 inches) of insulation. Alternatively, you could consider building with 11.5cm (4.5 inches) bricks.
However, you would then need to extend it all the way down to the ceiling and cut through the screed (probably existing), adding edge insulation strips properly.

A drywall partition wall above the screed is also a bad idea.
If you don’t inform yourself properly beforehand, it will turn into a noise disaster.

Search Google for "Knauf sound insulation – system solutions for every class."
The first result is a PDF file that compares several example constructions with masonry walls. Very insightful...

Thank you all for your opinions!

I actually looked up Knauf ...

However, it says there:

"Knauf metal stud walls consist of a metal substructure as a single or double stud frame and a one- or multi-layer cladding made from Knauf boards on both sides. The stud frame is continuously connected to the adjoining building elements. Insulation materials (for fire resistance requirements, prior coordination is recommended, see page 2) as well as electrical/plumbing installations can be installed within the wall cavity [B]."

It says "can be."

Specifically on sound insulation, it says a bit further:

"Sound insulation Avoid air leaks. For sliding connections, sealing with permanently elastic material (recommendation: Knauf Insulation LDS Solimur) may be necessary (see detailed drawings)."

Hmm, this doesn’t really clarify much for us. Avoiding air leaks sounds good since sound travels through the air. I also think decoupling the sound at adjoining building elements is important. But what about the insulation? Does it really make that much of a difference? Between two glass panes in a window, there is no insulation either... These are real questions we have about the wall construction.

Maybe someone has another idea on this?

Thanks in advance and best regards