When a car squeaks during acceleration, it is typically an indication that the fan belt has become loose or worn. A car's fan belt loosens over time and starts squeaking when the bottom section, which has rubber teeth, begins to drag.
A loose fan belt loses synchronicity with the pulleys that operate it, causing a loud squeaking noise. If the fan belt is loose, it should be retightened by a mechanic to avoid accidents. If worn, it may need to be replaced. When the fan belt is loose, there is a chance that the timing belt has also suffered some wear.