In My Bondage and My Freedom, why does a "silent slave" make masters and overseers uncomfortable?

tells us
that slaves were expected to sing as
well as work. The sight of fields of happy slaves
cheerfully toiling away in
the cotton fields while singing Negro spirituals was one that
slave-owners
were keen to promote as part of their idealized image of the peculiar
institution.
If slaves are silent or sullen, then they are inadvertently
challenging the romanticized
conception of slavery held by their owners and
overseers. It's important, then, for the slaves
to make some noise as they
work. Douglass says that silent slaves are always told to "Make
a noise
there! Make a noise there!"

There's also a practical reason
for
slaves being required to make noise. If they're working somewhere in the
distance, well away
from their overseer, then singing is a way of letting him
know where they
are.