|You're probably hearing noise caused by bearings that are in bad shape in one or more fan(s). The noise may be a rattling or rumbling sound if the bearings are worn enough to make the fan shaft wobble, and/or a screeching sound - most likely to be heard when you first start up the computer after it has sat unused foir many hours. |
If you have a laptop or netbook, it has only one fan - inside the case.
If you have a desktop computer, the noise could be coming from the CPU fan, or the power supply fan(s), or (a) case fan(s), or from a fan on a video card in a mboard slot, or if the mboard is older, from a tiny fan that's on top of one of the main chipset chips..
You could disconnect the power or fan header connector to a case fan to see if that's where the noise is coming from.
The noise from a power supply fan may be more obvious when you listen at the back of the case where it blows out air. Some power supplies have two or more fans.
A noisy CPU fan can be harder to determine. Most mboards will shut off in a very short time if there is no 3 or 4 wire fan connected to the CPU fan header. If you have a 3 wire case fan, you could try connecting that to the CPU fan header and disconnecting the CPU fan for a very brief time.
OR - If you place something solid between your head near your ear and the cpu fan, it may be obvious that's where the sound is coming from.
You may be able to unplug the connector to a video card fan on it's card (only do that briefly), or you can unplug any tiny fan that's on top of one of the main chipset chips (only do that briefly), to see if that's where the noise is coming from.
If you need to replace a fan.....
- try to get one that has two ball bearings or better (e.g. ceramic bearings). If the description or the labelling says ball bearing without an s, it's probably got one ball bearing, one cheap sleeve bearing.
- get a fan that is the same size or larger. Larger fans tend to make less noise from the airflow they produce.
- if it's the same size, the current rating or cfm rating of the replacment fan should be close to the same, or the cfm rating can be higher, or the current rating can be more (moves air at a faster rate).
- all fans used with computers suck in air on the side where you can see the entire fan blade, and blow it out the other side where you can't see the entire fan blade because there is a central non moving part and sometimes a support strut in the way.
A CPU fan (that's attached to the heat sink) MUST blow air towards the cpu heat sink. A PS fan MUST blow air out of the case. Most case fans should blow air out of the case, or (case side fans) towards the CPU heatsink or cards in slots. The best place to mount a single case fan is at the back of the case as high up as you can mount it, blowing air out of rhe case. .
Main chipset fans don't last long, Some cooling products makers, e.g. Zalman, have a heatsink you can install insteadl of the tiny fan.
If your video card has a tiny fan, they don't last long either. Some cooling products makers have a heatsink you can install instead of the tiny fan.
If a PS fan has only two wires, if you have a spare 3 pin fan header on the mboard, if you use a good quality (good bearings) 3 wire case fan of the same size you can run it's 3 pin connector's wiring outside of the PSs case and plug it into a 3 pin fan header on the mboard, and be able to monitor it's rpm, in the bios, or by using a hardware monitoring program in Windows.
- something inside your desktop case, probably a wire or cable, is touching a fan blade when the blade spins - move it.
- some optical (CD or DVD) drives are more noisy then others. the bios spins optical drives when they have a disk in them while booting and Windows spins the disk initially and at seemingly random times even when you're not actively using the disk, and sometimes when it does that the led on the front of it does NOT light up.
In any case, remove any disks you have in optical drives when you're not using them - since the drive will be spinning less of the time in Windows when you do that, your optical drive's motor cheap sleeve bearings will develop wear slower and the drive will be usable for a longer time.
- there may not be enough screws holding your hard and/or optical drives in place, or the screws may be too loose - that can cause rattling or buzzing noises from the metal of the case itself, or from the optical drives, due to vibration.