Now that I have taken a closer look at all components of an PC one by one and have given hints on how to get a handle on the noise each one makes individually, let's look at the one thing that has the potential to affect the noise output of the overall system in general: the case. If you already own a PC and are looking for ways to modify the case in order for it to let less noise leave the case overall, then the options are unfortunately very limited. At least under the assumption that you have already used your case with all covers mounted securely in place. All things considered, there is one rule that of course always applies: wherever air comes in, noise can come out. And where and how this noise is being generated we have already illuminated in detail in all the other sections before.
The main task of a PC case is to accommodate all the components of your PC and also case fans (or those on the radiator of a liquid cooling system) to generate the required air flow to prevent a heat death of all your expensive hardware. This airflow is usually directed that way: Intake at the front/bottom, Exhaust at the back or top. The alignment of the fans ensures that this works as desired. If you are not sure in which direction your fans move the air, then there is usually also an arrow on the side of their housings, which indicates the direction of the air flow.
A big mistake is to assume that you can get a PC to be quietest if you close off the front and let the fans on the back or top — that is, as far away from the user's ears as possible — just pull the 'hot air' out of the case. But of course, they can only suck out what comes in somewhere else. And closing off the front only ensures that the fans are forced to spend a lot of effort (read: high speed/loud noise) to pull the air out of all the gaps of your PC case. Therefore: if we want to pull hot air out of the case, then we also have to make sure that cold ambient air gets into the enclosure 'at the other end' and can flow past all the components that need to be cooled. For that reason, a relatively open case with good airflow will usually be significantly quieter for the same cooling performance as one that is well insulated, but in which the fans have to run at high speed to transport the hot air out of the housing at all.
But you should still not neglect the insulation of the case itself. The side walls made from thin sheet metal that are frequently used with inexpensive housings, can be considered themselves as kind of membranes, which will then
be able vibrate turn your PC case into a loudspeaker. In addition, the natural frequencies of uninsulated case panels are often in a range where they are excited by the vibrations generated inside. Therefore, when buying a new case, one
should pay attention to get one with thicker material for the side panels.
To improve the 'membrane situation' there are damping mats available, but from experience it is clear that light, cheap dampings are surprisingly ineffective, because they 'swallow' some some sound from the sound generated inside, but at the same time have little to no impact when it comes to the problem of the membrane effect present with too thin side walls. Even then, sound waves that are introduced into the housing (mostly from hard drives) are still radiated to the outside. For noise insulation is to be effective, it is best to use bitumen mats. These are heavy and can change the natural frequencies of the enclosure by enough (shifting them to lower frequencies) in order for them to no longer get excited as much by the spectrum of vibrations. A clearly better and more important measure is still to eliminate the noise problem at the source and to prevent the excitation by the installed hard disks. What you should consider in that regard I have described in a separate the section on the topic of hard disks.
When it comes to case fans, then the same applies here as it was already been discussed in the sections about water cooling and (case) fans above: ideally, select case fans that are as large as possible. Those will be able to provide the required airflow at as low fan speeds (read: low fan noise) as possible.
A side note on the increasingly fashionable silent cases in which the graphics card is installed vertically in front of a transparent side panel — most likely to be able to watch the (RGB) fans at work. This kind of the assembly I would advice against at present with most cases. The reason is that with this type of installation, the graphics cards are very often operated with very little distance to the case side panel and therefore the cooling of the graphics card suffers. And what does the graphics card have to do if one prevents it from access to the air required to breathe (cool): it will increases the GPU fan speed (read: the fan noise), in order to nevertheless still guarantee a sufficient air flow. So, from the point of view of noise, such a GPU installation is therefore not recommended, except for a few cases that really leave a lot of space between graphics card and side panel.
Date published: 16.06.2021