Stimulated Brillouin scattering is one of the predominant limitations for fiber-based narrowband lasers, amplifiers or passive transmission links. In addition to the output power limitation, stimulated Brillouin scattering imprints a broadband excess intensity noise on the signal for which several theoretical explanations have been reported. Some studies suggested the conversion from phase to intensity noise due to an asymmetric Brillouin gain spectrum. In this work we present new and consistent measurements of such asymmetric gain profiles and corresponding intensity noise spectra. Based on our results, we were able to reconstruct the shape of the measured excess intensity noise.