Blackout curtains and soundproofing
A common question asked is if blackout curtains help with soundproofing at all.
In a sense yes all blackout curtains will reduce sound in a way but it will vary greatly between the types of curtains and how they were made. A curtain panel being blackout most of the time means that no or less than 1% of sunlight can come through the curtains. This nicely also means that there is far less room for sound to go through the curtains with no resistance. However if the curtains are quite thin it doesn’t matter if they are soundproof or not as the curtain in general can’t stop any sound. There has to be some sort of layer of fabric to stop the sound. If a curtain lists specifics like foam backing and/or several layers of coating then it will provide at least some soundproofing.