Using double nanohole (DNH) optical tweezer setup and applying two lasers, we trapped and excited acoustic vibration modes of the PR65 subunit within the protein phosphatase 2A (PP2A). Our experiment shows that the vibrational modes are at frequencies of 24.26 GHz, 32.80 GHz, 48.47 GHz, 57.97 GHz which matches to the normal mode analysis results. This technique is single molecule and label free compared to typical methods used for characterization of biomolecules. Characterizing PR65 can be used as a paradigm for understanding the structural regulation of many repeat proteins.