"Foam earplugs" refers to small, soft pieces of material that are inserted into the ears to block or reduce noise and protect the ears from loud sounds. Full definition
It can be a good idea to use foam earplugs if you are stuck waiting for the express train. (theguardian.com)
These small earpieces are basically fancy earplugs, but instead of blocking all sound out as foam earplugs intend to do, they simply reduce the volume of certain frequencies in your surroundings. (entrepreneur.com)
These affordable earbuds will not muffle voices and music like some cheaper foam earplugs and they are durably constructed. (geekwrapped.com)