Yes, they can.
Soft materials for custom earplugs are more than just an option: they are strongly recommended, particularly in situations where the wearer is at risk of a blow to the head. In these cases, the use of a soft mold reduces the chance of ear injury.
There are several soft materials available for custom earmolds: soft acrylic, vinyl, and silicone. Of these three, vinyl is the most commonly used. It is firmer than silicone, thus gives the wearer more freedom in mold insertion and proper fitting in the ear. Unlike soft acrylic, vinyl does not absorb earwax and will not harden with time.
Earmolds made for hearing protection often come in bright fluorescent colors. This makes them clearly visible in the wearer's ear, signaling that the person's ability to hear and understand verbal instructions is significantly reduced.
Over-the-counter premolded flanged and formable earplugs are all manufactured from soft materials.
