I had a pavilion dv4-1430us for over a year, recently I started up the fan was very noisy like a bearing noise. what should I do? thanks for the advice

It sound like the CPU fan or server case fan/s or power supply fan bearings are worn.
To determine which fan/s is faulty open the computer case and stop each fan from spinning, one at a time to determine the noisy fan. Once you have identified the noisy fan then replace that fan.

Could be that dirt and dust have collected on the fins over the years and are throwing them out of balance. You could try cleaning the fins on the fan.

The bearings may also be wearing out.

15 years is a good life for a fan.

THE CPU IS AUTOMATICALLY CONTROLLED BY MOTHER BOARD. WHEN THE HEAT IS ON IT MOVES FAST AND AFTER COOLING IT WILL GET SILENT. U MAY CHECK IN CMOS SETUP FAN MODE

If it is the Fan Part# is 1-787-057-11 DC Fan.most of the time you can pull back and if fan is ok color wheel will make noise when going Bad.

The noisy fan is most likely caused by a worn/faulty bearing. This causes the fan to vibrate in the bearing and spin slower and therefore cause overheating CPU problems.
The CPU fan needs to be replaced.

the electric motor bearings and/or brushes have worn. soft metal screws is an indication of the quality of the motor.not good. sometimes units are of nice design, look and high price but they throw in a cheap chineese motor. all you can do is put a few drops of oil on the motor bearings, its ok to do when this worn out

It could very well be the noisy fan. Try tapping the computer lightly to see if the noise stops or changes to confirm if it indeed is the fan. Or it could be a noisy HDD.  There is nothing you can do about a noisy HDD but about a noisy fan you can stop worrying as it will cause no probs as long as it is working, noisily or otherwise. You will have to tolerate it. Sometimes it is the detatchable sides of the computer (you wrote 'computer' in your question). See if the noise stops or lessens when you touch the sides a little harder.

If the fan was working correctly, and is now making a noise it's probably a bearing/lubrication issue on the fan itself.

If the laptop is only 1 month old I would take it back.

The sound you are hearing is probably the fan, This fan has a noisy bearing and will eventually lock up and the fan will stop spinning and therefore the CPU will overheat and shutdown.
The fan needs to be replaced.

If it is a fan assisted oven , then it sounds like a noisy oven fan.
It could be a worn or dry bearing in the fan motor. if you open the oven door , you should be able to tell if it is the fan by listening to it carefully.
The other possibility is if it has a cooling fan in the back or on the top of the oven, it could also be that causing the prob, these are about the only things that could be making a noise, as there are no other moving parts that could make a noise.
PLz rate my solution.

Thanks.