This is equivalent to installing a pair of ported baffles in an acoustic pipeline.
Elimination of compliance for a 2 in. section of the water wave channel is accomplished by eliminating its free surface. A short section of 1 in. square pipe set into the filter section of the water wave channel provides the power attenuation curve of Figure 22. There is a first harmonic full choke, a full pass for the second harmonic, and a full choke of the third and above.
Because the compliance area does not equal the inertial area, there is no acoustic analog to this experiment.
Changing the value of inertance while retaining the value of compliance of the water wave channel is accomplished by increasing its underwater wall width. The underwater width is increased 50% and the free surface width is unchanged by the filter element which produces the power attenuation curve of Figure 23, There is a full choke with the first harmonic and a full pass with the second. There is a partial choke at the third harmonic wavelength and full pass for anything above.
Because the compliance area does not equal the inertial area there is no acoustic analog to this experiment.
|