My house has a 600mm drop from the drain grate to the sewage line below. When having a shower the drain echo was louder than the shower head and water!

This is sized to almost completely fit the drain pipe diameter and sits atop a cut length of PVC tube so that the silencer sits just below the shower grate.

This has, in my showers, reduced the noise by 90%.

The holes around the perimeter are designed to provide an overflow path if the water flow becomes large. The centre hole is designed to allow a long bent wire to retrieve the silencer should it ever need to be removed.

When printing, have the mushroom sitting upside down on its head with the stem upwards. I used a snug baseplate only support. The support needs to be quite tight to the object to prevent failures.

I acetone smoothed it to stop any water ingress to the print and future mould problems.