Acoustic analog to multiple avoided-crossings in two coupled acoustic cavities

A cylindrical pipe with closed ends and with a partition in-between exhibits acoustic modes in the two, thus formed, one-dimensional cavities at certain frequencies. A partial transmission through the partition leads to interaction between the two cavities' modes and to multiple avoided crossings between modes' frequencies as a function of the partition position. This is analogous to a quantum system that has two multi-level and interacting sub-systems and thus exhibits multiple avoided crossings. Such an acoustic analog is realized and studied by measuring the sound transmission as a function of frequency through a pipe with a partially transmitting and movable partition. An excellent agreement is obtained between the experimental results and a simple model based on sound wave transmission and reflection at different interfaces.