Accuracy of Brillouin frequencies for material characterization by light scattering

We describe the method that allows us to give an estimation of the uncertainty on the frequency peak by Brillouin Light Scattering. It is the speed of phonons in a material excited by a visible green 532 nm wavelength laser. We follow the Guide to the Expression of Uncertainty in Measurement to obtain a first estimation of the speed of the phonons at ±5 % at 2 σ.