We experimentally study forward Brillouin scattering in tapered fibers. Circularly symmetric acoustic phonons resonant in fibers are observed by using a novel photoacoustic measurement technique. Strong acousto-optic interaction can take place in highly tapered fibers. © 2008 Optical Society of America. Dainese, P., Russell, P.S.J., Wiederhecker, G.S., Joly, N., Fragnito, H.L., Laude, V., Khelif, A., Raman-like light scattering from acoustic phonons in photonic crystal fiber (2006) Opt. Express, 14, pp. 4141-4150Elser, D., Andersen, U.L., Korn, A., Glöckl, O., Lorenz, S., Marquardt, C., Leuchs, G., Reduction of guided acoustic wave Brillouin scattering in photonic crystal fibers (2006) Phys. Rev. Lett., 97, p. 133901Beugnot, J., Silvestre, T., Maillotte, H., Mélin, G., Laude, V., Guided acoustic wave Brillouin scattering in photonic crystal fibers (2007) Opt. Lett., 32, pp. 17-19Shelby, R.M., Levenson, M.D., Bayer, P.W., Guided acoustic-wave Brillouin-scattering (1985) Phys. Rev. B, 31, pp. 5244-5252