Maestro
12-15-2005, 03:29 PM
I thought it might be good to start a sort of "how-to in-principle" guide, to get a collection of all the basics on how to silence a PC and why the methods are effective, both for our own brain-picking and for the benefit of the few people actually wandering over to this section of the forum and wondering what it's about...
Decoupling--This is a big one. Anything with moving parts has the potential to create vibration. Decoupling fans, hard drives, CD drives, waterpumps, etc will help prevent them from transferring their vibration to the case. The case is where you REALLY want to be vibration free, as a vibrating case can produce rattling sounds, and the big panels just act as big diaphragms and turn all that vibration into noise. So, the solution is to detach these pesky devices from everything else by essentially suspending them with silicon/rubber grommets, bungies, levitation, etc.
Reduce Air Speed--All other things being equal, an 80mm fan moving 30cfm will be louder than a 120mm fan moving 30cfm, I think we all know this. This is due to a couple things; first, and most obviously, the 80mm fan will need to spin faster, creating more turbulence, motor noise, and "whistle" from the blades cutting the air. Additionally, an 80mm fan needs to attain greater air speeds. For an 80mm fan to put out 30cfm, it needs to push an 80mm column of air at 554ft/min, while the 120mm fan needs to push a 120mm column of air at only 246ft/min. Now, airspeeds will drop right beyond the fan, as the air column effectively expands in diameter leaving the confines of the fan housing, but this still gives a pretty good idea of the air speeds directly in front of and behind these different size fans, so you can imagine the difference in noise level that would be caused by this air hitting an obstruction (grill, heatsink) at either 554ft/min or 246ft/min.
Reduce Air Volume--If you have two air column moving at equal speed, but one is 80mm across and the other is 120mm across, obviously the 80mm column is going to cause less noise and turbulence when hitting obstacles. This also loops back to the air speed above if you are dealing with a fixed-size constraint on your intake/exhaust. Say you have an exhaust port of a fixed size. Then you replace an 80mm intake fan moving 20cfm with a 120mm intake moving 30cfm. You may not cause increased noise at the intake, but you've increased volume, and therefore increased airspeed (and potentially noise) through your fixed-size exhaust. The lesson? Only move as much air as you need to, and no more. Go passive where you can.
Reduce Turbulence--related to air speed and volume is turbulence, another noise culprit. Reducing speed and volume will help, but also remove obstructions such as fan grills and gratings. The finer the grating or fan grill the more likely it is to make noise. Open space is your friend--it reduces turbulence and reduces air speed by increasing area.
Baffling--Block those sound waves! Anywhere there is a direct path between the noise source and the air outside of the case, there is room for improvement. Think of it like line-of-sight--you put something in front of the lamp and you don't see the lamp anymore. That said, sound waves don't adhere to a straight line like light does, but it's the same basic idea. Covering exhaust or intake ports with a convoluted maze will help prevent sound from escaping by absorbing, redirecting, and canceling it. Keep in mind though that baffling has the potential to cause some noise also by creating air turbulence.
Adding Mass--Sound waves have a finite amount of energy. Sound that may transmit through a cheap aluminum side panel may not have the power to transmit through a steel side panel that weighs eight times as much, or even a good quality aluminum one that weighs three times as much. The same goes for vibration--the higher the mass of the target object, the less vibration it will ultimately transfer to the air or to your desktop. Really, what you want is for the ratio of vibrating mass (ie, fan blades, hard drive) to anchoring mass (ie, fan housing, hard drive bay) to be as low as possible, but since it's far easier to add mass than it is to remove it from fan blades or hard drives, the anchoring mass is really the only side of the equation most people will need to worry about.
Sound Dampening Materials--"Soundproofing" materials designed to cancel and absorb sound waves can help to reduce the amount of noise bouncing around inside the case and reaching your case panels, case openings, and ultimately your ears. These materials vary greatly in effectiveness and function. Some are very light and work mainly by absorption and cancellation, others are heavy and work by absorption and cancellation and/or simply adding mass. Some work, some don't.
Components--Quiet components are usually quieter than components that are louder than said quiet components, so do your research and choose accordingly.;)
Decoupling--This is a big one. Anything with moving parts has the potential to create vibration. Decoupling fans, hard drives, CD drives, waterpumps, etc will help prevent them from transferring their vibration to the case. The case is where you REALLY want to be vibration free, as a vibrating case can produce rattling sounds, and the big panels just act as big diaphragms and turn all that vibration into noise. So, the solution is to detach these pesky devices from everything else by essentially suspending them with silicon/rubber grommets, bungies, levitation, etc.
Reduce Air Speed--All other things being equal, an 80mm fan moving 30cfm will be louder than a 120mm fan moving 30cfm, I think we all know this. This is due to a couple things; first, and most obviously, the 80mm fan will need to spin faster, creating more turbulence, motor noise, and "whistle" from the blades cutting the air. Additionally, an 80mm fan needs to attain greater air speeds. For an 80mm fan to put out 30cfm, it needs to push an 80mm column of air at 554ft/min, while the 120mm fan needs to push a 120mm column of air at only 246ft/min. Now, airspeeds will drop right beyond the fan, as the air column effectively expands in diameter leaving the confines of the fan housing, but this still gives a pretty good idea of the air speeds directly in front of and behind these different size fans, so you can imagine the difference in noise level that would be caused by this air hitting an obstruction (grill, heatsink) at either 554ft/min or 246ft/min.
Reduce Air Volume--If you have two air column moving at equal speed, but one is 80mm across and the other is 120mm across, obviously the 80mm column is going to cause less noise and turbulence when hitting obstacles. This also loops back to the air speed above if you are dealing with a fixed-size constraint on your intake/exhaust. Say you have an exhaust port of a fixed size. Then you replace an 80mm intake fan moving 20cfm with a 120mm intake moving 30cfm. You may not cause increased noise at the intake, but you've increased volume, and therefore increased airspeed (and potentially noise) through your fixed-size exhaust. The lesson? Only move as much air as you need to, and no more. Go passive where you can.
Reduce Turbulence--related to air speed and volume is turbulence, another noise culprit. Reducing speed and volume will help, but also remove obstructions such as fan grills and gratings. The finer the grating or fan grill the more likely it is to make noise. Open space is your friend--it reduces turbulence and reduces air speed by increasing area.
Baffling--Block those sound waves! Anywhere there is a direct path between the noise source and the air outside of the case, there is room for improvement. Think of it like line-of-sight--you put something in front of the lamp and you don't see the lamp anymore. That said, sound waves don't adhere to a straight line like light does, but it's the same basic idea. Covering exhaust or intake ports with a convoluted maze will help prevent sound from escaping by absorbing, redirecting, and canceling it. Keep in mind though that baffling has the potential to cause some noise also by creating air turbulence.
Adding Mass--Sound waves have a finite amount of energy. Sound that may transmit through a cheap aluminum side panel may not have the power to transmit through a steel side panel that weighs eight times as much, or even a good quality aluminum one that weighs three times as much. The same goes for vibration--the higher the mass of the target object, the less vibration it will ultimately transfer to the air or to your desktop. Really, what you want is for the ratio of vibrating mass (ie, fan blades, hard drive) to anchoring mass (ie, fan housing, hard drive bay) to be as low as possible, but since it's far easier to add mass than it is to remove it from fan blades or hard drives, the anchoring mass is really the only side of the equation most people will need to worry about.
Sound Dampening Materials--"Soundproofing" materials designed to cancel and absorb sound waves can help to reduce the amount of noise bouncing around inside the case and reaching your case panels, case openings, and ultimately your ears. These materials vary greatly in effectiveness and function. Some are very light and work mainly by absorption and cancellation, others are heavy and work by absorption and cancellation and/or simply adding mass. Some work, some don't.
Components--Quiet components are usually quieter than components that are louder than said quiet components, so do your research and choose accordingly.;)