The acoustic modes propagated in the bc plane of triclinic beta -BiNbO
4 single crystal are investigated by the Brillouin scattering method a
t room temperature. The Brillouin spectra corresponding to the longitu
dinal acoustic mode are analyzed to evaluate the elastic constants. Ob
tained elastic constants are c33=16+/-2, c22=27+/-3 and C23+2C44=25+/-
3 in the unit of 10(11) dyne.cm(-2).