A modular damper plug forming a multi-volume acoustic resonator in an acoustic liner of a rocket engine is provided. In one aspect, the damper plug includes a main body including a top surface spaced from a bottom surface by a first height, a left surface spaced from a right surface by a width, and an exterior surface spaced from an interior surface by a length. A chamber within the main body extends along a part of the height, a part of the width, and a part of the length, and communicates with the top surface through an opening. The chamber also communicates with the interior surface through one or more ducts. The main body is sized and shaped to be received in any one of a plurality of cavities in the acoustic liner. The chamber includes an upstream volume of the acoustic resonator, and the one or more ducts communicate with a downstream volume of the acoustic resonator when the damper plug is received in any one of the plurality of cavities.