Help with the Kundt's Tube Apparatus?

Question

I'm working with the Kundt's Tube Apparatus, and when the experiment is complete, inside the tube there's nodes, but at the nodes are many smaller lines (around 20 or so per node, about 1 mm apart [the larger nodes are around 4.5 cm apart) and I'm wondering what these lines are. I can't seem to figure it out.

Thanks for any help with this, It'll be much appreciated.

Answer 1

They are most probably higher harmonics. Higher harmonics sound waves are surely present in the tube and they will create additional accumulation of cork dust that will be more closely spaced than the main ones, and they will be of smaller amplitude.