  Striped phases in which spin and charge separate into different regions in
the material have been proposed to account for the unusual properties of the
high-$T_c$ cuprate superconductors. The driving force for a striped phase is
the charge distribution, which self-organizes itself into linear regions. In
the highest $T_c$ materials such regions are not static but fluctuate in time.
Neutrons, having no charge, can not directly observe these fluctuations but
they can be observed indirectly by their effect on the phonons. Neutron
scattering measurements have been made using a specialized technique to study
the phonon line shapes in four crystals with oxygen doping levels varying from
highly underdoped to optimal doping. It is shown that fluctuating charge
stripes exist over the whole doping range, and become visible below
temperatures somewhat higher than the pseudogap temperature.
