  The walls of bubbles in a first-order phase transition can propagate either
as detonations, with a velocity larger than the speed of sound, or
deflagrations, which are subsonic. We calculate the gravitational radiation
that is produced by turbulence during a phase transition which develops via
deflagration bubbles. We take into account the fact that a deflagration wall is
preceded by a shock front which distributes the latent heat throughout space
and influences other bubbles. We show that turbulence can induce peak values of
$\Omega_{GW}$ as high as $\sim 10^{-9}$. We discuss the possibility of
detecting at LISA gravitational waves produced in the electroweak phase
transition with wall velocities $v_w\lesssim 10^{-1}$, which favor electroweak
baryogenesis.
