<Moderator's note: Moved from a technical forum and thus no template.>
I've done an experiment on standing waves on a string.
By graphing √T vs λ (where T is tension and λ is wavelength) using the linearized equation √T = (1/√μ) f ⋅ λ, I was able to get this data:
μ = .000256 kg/m
slope = 1.78...