Pipe natural frequencies are dependent on the geometry of the pipe where the pipe length is the main
contributor in regulating the natural frequencies. The boundary conditions are another major
contributor because the acoustic waves in the pipe will produce standing waves because of the
reflections at the boundary conditions. Making one of the boundary conditions location in the pipe
adjustable will allow for the length of the pipe to be modified and therefore change the natural
frequencies of the pipe. This adjustable pipe provides a means for introducing undergraduate
students to an inexpensive setup to test pipe length in changing the natural frequencies of pipes
and the associated sound pressure level within the pipe. Helmholtz resonators are passive devices
that can absorb acoustic energy from an acoustic enclosure. These resonators have three major
variables that are used to determine the resonant frequency of the resonator and therefore the
frequency at which the resonato…