Hearing protection devices and kits may include an earplug body and an adjustable sound attenuation assembly composed of an attenuator case and an attenuator insert that is removably insertable into the attenuator case. The attenuator case has a hollow barrel portion that accommodates the attenuator insert and a hollow extension portion connected to the hollow barrel portion. The hollow extension portion includes a soundpath channel therethrough defining a soundpath axis. The attenuator insert is rotatable within the hollow barrel portion of the attenuator case about a rotation axis that is noncollinear with the soundpath axis. The attenuator insert has a thickness along the soundpath axis that varies with respect to a rotation angle of the attenuator insert within the attenuator case. Thereby, sound waves that enter the soundpath channel through the distal opening are attenuated proportionally to the thickness of the attenuator insert along the soundpath axis.
