  In this letter we study the generation of gravitational waves during
inflation from a 5D vacuum theory of gravity. Within this formalism, on an
effective 4D de Sitter background, we recover the typical results obtained with
4D inflationary theory in general relativity, for the amplitude of
gravitational waves generated during inflation. We also obtain a range of
values for the amplitude of tensor to scalar ratio which is in agreement with
COBE observations.
