One way to silence a squealing belt on a car is by spraying on a belt dressing. Belt dressing works as an adhesive to increase the friction between the belt and the pulley to help extend the life of the belt.
Car belts typically do not begin to squeal unless they are worn out or they are not tight enough. Once a belt starts squealing it is best to have it replaced. While a belt dressing can offer a temporary fix while the driver is on the road, the belt is sure to squeal again soon before it finally gives and breaks.