Customized hearing protection earplug and method for manufacturing the same

A hearing protection earplug to be worn at least in part in a user's ear canal, comprising a shell having an outer surface individually shaped according to a measured inner shape of said user's outer ear and ear canal, and a functional member engaging said shell in a manner so as to be movable relative to said shell between a first functional position and a second functional position, said shell and said functional member having an elasticity of between shore D85 and D65, wherein said functional member is adapted to change the outer shape of said shell when being moved from said first functional position to said second functional position in order to provide for an acoustic attenuation of at least 10 dB averaged over an audible frequency range when worn at least in part in said user's ear canal, wherein said shell comprises an axial portion in which the thickness of an outer wall is reduced relative to a remainder of said shell in said first functional position thereof in order to cause said outer wall of said axial portion to bulge outwardly upon movement of said functional member from said first functional position into said second functional position, and wherein said functional member is adapted to axially compress said shell when being moved from said first functional position to said second functional position to produce said outward bulging of the outer wall of said axial portion.