It maybe your suspension that squeaks when ever you go over the speed bumps.
Squeak in tires (when turning in particular) could mean low tire pressure, or bald tires.
Loose shock absorbers
bad shocks or struts
Both ends
Replace all 4 ball joints for less than $20 a piece. you'll probally be charged less than $125 to put them on. total $205 I assume you asked about it doing it turning also. Ball joints can't be the problem in both cases. Turning may just be the tires on the pavement. Squeaking on bumps could be a dozen different things in the front end depending on the type of squeak and how loud. Type of car, front or rear wheel drive makes a difference also.
The wheel bearing.
More info: '97 Honda, the right front tire was recently patched by a tire shop. Squeak occurs when the car bounces on bumps, holes, rough road.
Defective rear shocks. Loose exhaust components.
If the struts are bad on any vehicle, including the Kia Optima, the automobile is going be very bouncy going down the road. The car will start to bounce and it will seem like it is never going to stop bouncing, even with the tiniest of bumps. It might also squeak when going over bumps.
A lot of times the grinding sound that is heard when going over bumps is actually the car scraping the cement. If it is not a serious problem then the best thing to do would be to drive slow over the bumps.
Most likely a bad tire.
The squeak is your tires losing traction on the pavement. Prominent in rear wheel drive cars.