Correction to: Scientific Reports https://doi.org/10.1038/s41598-017-11000-x, published online 05 September 2017

This Article contains errors in Equation 1.

$${f}_{o}=\,\frac{1}{2L}\sqrt{\frac{\sigma }{2L}}[{\rm{Hz}}]$$

should read:

$${f}_{o}=\,\frac{1}{2L}\sqrt{\frac{\sigma }{\rho }}[{\rm{Hz}}]$$