The announcing move is less commonly used, and at the undergraduate and master's level, it's probably unnecessary unless you feel particularly strongly about including it. Students that do include it tend to use it to either accept responsibility for their work and/or dedicate the dissertation to someone. Dedicating the work is fine, but it's probably no longer necessary to accept responsibility for your work in the acknowledgement section. After all, because of the increasing focus on plagiarism, you're often expected to include a separate sheet in your dissertation declaring that the work and ideas are all your own anyway. So there's little point repeating yourself here.
Hyland, K. (2003). Dissertation acknowledgments: The anatomy of the Cinderella genre. Written Communication, 20(3): 242-268.
Hyland, K. (2004). 'Graduates' gratitude: The generic structure of dissertation acknowledgments. English for Specific Purposes, 23: 303-324.
Hyland, K., & Tse, P. (2004). "I would like to thank my supervisor". Acknowledgments in graduate dissertations. International Journal of Applied Linguistics, 14(2): 259-275.
Mingwei, Z., & Yajun, J. (2010). Dissertation acknowledgments: Generic structure and linguistic features. Chinese Journal of Applied Linguistics, 33(1): 94-109.