Any time I accelerate, something under the hood makes a screeching noise...sometimes louder than others. It sounds like a belt wearing

try this.
Diagnosing Belt Noise squeak or squeal on Serpentine Belt

Check ur fan belts/ serpent belt .open hood you stand in front of car have someone start it and see if make noises

Have the accessory drive belt checked and the automatic tensioner for that belt.

If its a knocking sound:

A KNOCKING SOUND IN THE ENGINE IS MOST LIKELY CAUSED BY ONE OF THE FOLLOWING
1. PISTON SLAP: Makes a sharp metallic noise. Idle engine and short out each cylinder plug. The noise will disappear when plug with bad piston is shorted. Noise will also disappear at acceleration. This can be caused by worn or out of round cylinder, or broken piston ring. Correct problem by re-boring cylinder and/or replacing piston.
2. VALVE NOISE: Makes clicking or rattle noise. Caused by excessive wear on valve stem or lifter, out of adjustment, or stuck valve. Correct by adjusting valve clearance, replace worn valve or lifter, regrind cam, replace valve guide and /or valve. A stuck valve can sometimes be loosened by passing oil through the carburetor while engine is running.

3. ROD BEARING KNOCK: Makes sharp metallic noise similar to a piston slap. Detection is opposite of piston slap. Rod knock is not heard at idle. Knock becomes louder as engine speed is increased. Caused by excessive rod bearing clearance. Correct by adjusting rod bearing clearance to .0015 inches by removing shims. May require re-pouring rod bearing.
4. REAR MAIN BEARING KNOCK: Makes dull knocking or thud noise. Detected at speeds between 20 and 50 MPH. Knock will normally decrease or disappear while pulling or decelerating. Noise will be detected the loudest at normal driving speed, when not pulling or decelerating. Correct by adjusting bearing clearance to .001 to .0015 inches. If knock is excessive, crank should be checked for out of roundness. May need to re-pour all main bearings to correct.
5. TIMING GEAR KNOCK: usually the most difficult to diagnose. If gear is loose or badly worn it will knock in all ranges. Run engine slightly above idle speed. Slowly open and close throttle. Knock will continue to be present, but just as engine slows down knock will become a slight rattle. Remove timing pin and reinsert into timing hole on timing gear cover. Press timing pin tightly against timing gear and accelerate slightly above idle. Knock will significantly be reduced or disappear. Correct by replacing both timing gear and crank gear as a matched set. The two gears should have a backlash clearance of .003 to .004. If more than .009 inch backlash, an oversize (.005) timing gear should be installed.
6. WRIST PIN SLAP: This can not be detected by shorting out the cylinder plugs. Rapidly accelerate and decelerate the engine speed. The engine will pass through a certain speed range when the wrist pin will rattle at about the same pitch as a valve tappet noise. This can be corrected by installing a new wrist pin bushing in the rod or new wrist pin f badly worn. Wrist pin should fit the piston and connecting rod with a tight metal to metal fit. The pin can be pushed into the piston and rod with a slight pressure of the hand. Pin to rod clearance is .0003 to .0005 inches.

Could be a belt screeching. Fan belt, A/C belt, Serpentine Belt, alternator belt, etc. Easiest way to isolate which belt is to open the hood and use your ears to see where the screeching is coming from. Left, right, front, behind the engine? Spray some WD-40 on the belt you think is making noise and if it quiets right away, then that is the belt making the noise. Either the tensioner needs adjusting or the belt needs replacing. The WD-40 does not hurt the car, it'll start screeching again in a few days when it wears off.

the noise is coming from the wheel section, it's called air splash, humming varies with speed, main causes are wheel alignment due to loose ball joint, check if your tire erodes on one side, next check your disc brake for clogged air cooled vain and disc wearing

It probably is a belt. You should look under the hood and check for a loose belt. Tighten as necessary. You should not be able to deflect the belt more than 1/2" in the center of the span of the belt.

Brakes will also make a screeching noise when they are worn out. This noise will also go away when you stop (of course). The sound is quite different than the belt sound.

What type of sound is it first off? It could just be brake dust. Alot of people dont know that brake pads have a little metal piece on them thats sort of like a sensor,when the pads wear down past a certain point the little metal piece starts to scrap the rotor which will make a screeching noise.The more the pad wears down the louder and more annoying the sound becomes.

i would have to say that the timing belt is worn and stretched out for normal wear and tear. The check engine light is probably for the same reason. If the timing belt is not quite right it will throw a timing code for the camshaft being out of sync due to the excess slack that is in the timing belt.

Sounds to me like you need the alternator idler pulley. Look at it and see if it has a big washer covering portion of the pulley, or if the washer is inside the pulley. If its inside, than you have an old pulley. Replace it with the one, that has the big washer in the middle of pulley. You do have another idler for the A/C compressor. Those I have seen fail also. But 80% of the time its the alternator idler pulley.