Soundproofing for laundry chute

Even if it is not 100 percent soundproof, laundry doesn't fall down there all day long, just briefly once in a while....

You are factually right. The main point here is to ensure that the system does not serve as a means of sound transmission for other noise sources. It’s annoying, for example, if impact noise is amplified by insufficient decoupling or if you end up with an unintended multi-room music system as soon as a radio is playing somewhere.

Even if it’s not 100 percent soundproof, laundry doesn’t fall there all day, just briefly once....

But the thing is a conduit through the entire building without insulation??? Noise from the utility room into the room where the laundry is thrown? That’s what it’s about, not the laundry...

Then build a soundproof flap in front of it.

Last week, someone here cared most that the sound in the laundry chute should above all be germ-free

In principle, this pipe is a simple telephone, and only by preventing the sound flowing through it does the air column inside become truly efficient. Transmission through the vibration of the pipe itself is not reliably dampened by stuffing its opening or component penetrations since fastenings still remain prime transmitters. What is it even about: fear that the clattering of the spinning washing machine penetrates into the sleeping area and possibly even gains amplification from the pipe as a resonance body?

In most cases, it will probably be kindly classified as a luxury problem caused by a non-hermetically sealed "connecting pipe" that affects living quality – in particular, only premium sensitive people will notice this. That the family cannot sleep because the dryer whispers will likely be considered a disaster.

It is more about the transmission of sound through the opening around the pipe. That the pipe itself transmits sound is obviously clear to me.

As I tried to explain above, the flowing sound even reduces the transmission quality of the air column in the pipe and additionally delights with a broader spectrum. That means this sound does not have such a defined peak at any frequency as the one that goes through the pipe (because the pipe has one inner diameter = one resonance frequency = one particularly well transmitted area within the spectrum, while around it it is much more colorful but nowhere particularly loud). Therefore my conclusion is that you are dealing here with a philosopher's problem rather than a relevant practical problem, and you can therefore relax, even without confronting the sound heavily armed.