I installed my infinity 465a and when I listened to it on accessory it sounded great. Unfortionately when I started my car up I noticed a whine that increased as the rpms increased.

Without more info. All i can suggest is get a stethoscope, or lenght of rubber tube, and place in vicinity { BE CAREFUL} of noise. Shine light & see if you can notice the pulleys { where the belt goes] moving smoothly. Notice any pulleys that may be moving a bit erratic at idle

Sometimes this happens and you may have to cycle the switch back to off then go to the start position. Running a radio from the on position is not a good idea as there is still current going through the ignition circuit and this will burn out coils . You should be using the accessories position to listen to the sound equipment and if it is not working in that position then it might be a good idea to get it fixed.

The best way to find noise is a thesescope can get at automotive store put on each component and listen for noise To me I know you said new alternator but sound like the rectifier in alt disconnect the alt wireing and listen also check the idler pulley bearings Dose the truck have AC Take the AC belt of and try it as its a seperate belt

I'm going to say it is a main shaft bearing that is wearing out, much like a differential or axle bearing.
You might do some online research for that model and see if it is a common problem with other owners.

Could be several things.
You could take a section of heater hose and use it like a stethoscope to listen for the noise while the engine is running.
Once you narrow down the location you could take the belt off for that accessory to confirm.

he may need an adaptor to run to the infinity amp. it should be available at any good car audio store.

Turn key forward and listen for the fuel pump to kick on. It will make a high pitched sound then shut off. If no sound the more than likely you need a fuel pump. You can check at the fuel rail with a guage pressure should be 30psi.

There is a fan insine the power supply, and also a fan on the CPU. Occasionally there is also a fan on the chassis of the computer itself.

Turn on the computer, take the case off, and listen to identify the source of the noise. If it's inside the PSU, return it and get a new one.

The Power Steering cannot only go out when in Reverse. You must have a Problem with it going both Ways. Do some driving and a Lot of turning. Listen for a Whine or Clicking from the Power Steering Pump.

Check the condition of front disc brake pads, if they are in need of replacement a preset little metal arm starts rubbing the discs and will make a whining noise. It doesn't do any damage but it's irritating to listen to.