  Our aim in this work is to outline some physical consequences of the
interaction between black holes and scalar field halos in terms of
gravitational waves. In doing so, the black hole is taken as a static and
spherically symmetric gravitational source, {\it i. e.} the Schwarzschild black
hole, and we work within the test field approximation, considering that the
scalar field lives in the curved space-time outside the black hole. We focused
on the emission of gravitational waves when the black hole is perturbed by the
surrounding scalar field matter. The symmetries of the spacetime and the
simplicity of the matter source allow, by means of a spherical harmonic
decomposition, to study the problem by means of a one dimensional description.
Some properties of such gravitational waves are discussed as a function of the
parameters of the infalling scalar field, and allow us to make the conjecture
that the gravitational waves carry information on the type of matter that
generated them.
