What caused older computer fans to be so much louder than they are today?

Question

I had one of those bulky IBM 486 PCs in the mid-1990s. Desktop form factor. I think it was probably made somewhere in 1992. It made a lot of noises, pleasant ones to me, such as mechanical hard drive ones, or the floppy disk station doing "its thing" (whatever that really was).

But most of all, there was a loud "humming" or rather "buzzing" noise coming from it constantly while powered on. I never really thought about what exactly made that sound back then, but of course it was the one general fan inside. The CPU only had a passive heatsink.

I don't still have it to verify anything, or to listen to it now, but I do remember it felt ancient even in the late 1990s when I had got a brand new PC which, in comparison, was quite futuristic even though only a few years had passed. It was certainly much less loud.

Clearly, they invented some sort of sound muffler technology for fans between the dates when those computers were made, just a few years apart. But what exactly was that? How can you make something so simple as a fan in different ways? It just gets electricity (no noise from that) to power a plastic blade that spins around with some kind of little engine. How can the difference in sound be so massive? Especially if you compare it to the computers we have now, which are almost eerily quiet.

I doubt there was something wrong with the fan in it, as I had been around other loud PCs, but maybe it was "built to a cost" and thus not the best that could be made even back then? I don't understand what they could have changed to make computer fans so much less noisy.

(I doubt that the various chips made any noises.)

Answer 1

Maybe heatsink technology made progress, but one of the reasons is adaptative fan speed.

Modern PCs have temperature sensors on main chips, and the firmware of the boards (or the BIOS, or UEFI, whatever) increases fan speed only when needed, not all the time.

So even if the fan makes the same noise, it's not running at full speed all the time, only when there is intensive CPU/GPU computation.

Answer 2

Anything that moves generally tends to make noise, and the faster it moves the more noise it makes. So perhaps a better question would be not what caused the older computer fans to be so much louder, but what caused the newer computer fans to be so much quieter.

While @StephenKitt addressed the reasons that drove making fans in the PCs more quiet in his excellent answer, I'd like to focus more on how exactly they were made more quiet.

Generally, the noise type and level a fan makes is determined by several factors:

• the hub bearing type and construction
• the blades' shape, size, and number
• the rotation speed
• any obstructions in the air flow
• case design

The bearings - older fans were more likely to use simple sleeve bearings, which wear out quickly and as they wear out they start making more noise. The type of noise is more likely to be of rattling or buzzing quality, and likely to change with temperature - e.g., my parents' old computer would be buzzing like crazy when just turned on, but after a few minutes of run time and a slap on the case it would quiet down. The modern fans (especially the more expensive variety) are more likely to use ball bearings, which last longer and run quieter.

The blades - believe it or not, there has been some research put into developing blade shape that would be as efficient as possible, and besides improved airflow it also translates into less energy wasted on vibrations, A.K.A. noise. The fan blade shape has changed a lot since mid-late nineties and until now, especially in laptops. As was already mentioned, the fans have become bigger too, which translates into...

...Slower rotation speed, even at the top air mass flow. Plus, the fan speed is not constant, but typically controlled based on the air flow need, even in PSUs (power supply units) - e.g., in my EVGA Supernova PSU the fan may not even kick in at all until the PSU temperature exceeds 55 degrees Celsius, similarly to my Noctua CPU fan. And then when they do kick in they will start off slow and speed up as the air flow need increases. That's why most computers nowadays are really quiet at idle but become progressively more noisy the heavier their workload gets.

Any obstructions in the air flow are likely to cause turbulence and vibrations, which translates into noise. These things can be a bit of a hit and miss even in a modern bespoke PC, but nowadays you're more likely to see at least some thought put into airflow management during case design, especially for factory-built PCs by big-brand manufacturers like Dell/HP/whathaveyou.

Finally, earlier PC cases were often made of just simple sheets of metal. The more expensive ones would have thicker and sturdier metal, and cheaper ones would have more flimsy metal. Those cases would often act as a sound box, amplifying the sound of fans (or anything else inside, really), so the cheaper, more flimsy ones would amplify more. Modern cases (or at least the ones I've dealt with recently) tend to have some dampening around the side panels, or be made out of acrylic and other materials that tend to absorb sound more instead of amplifying it. Besides raw materials they are also overall designed better these days.

Answer 3

Other answers address fan construction and fan control. I think it’s also important to consider the overall system design and target audience.

Early PCs, in fact PCs until the late 486 and Pentium era (early to mid 90s) typically had a single fan, which had to take care of all the ventilation requirements of the system, not only as built, but as the user might end up equipping it. This single fan was included in the PSU, which restricted its size, and required a higher speed to produce a given airflow than is possible with today’s 12cm-fan-equipped PSUs. Furthermore, while PCs themselves had smaller thermal envelopes than today’s PCs, the PSUs themselves were far less efficient than those available now.

The target audience probably also played a part, at least for the first PCs. Contemporaneous home micros had no fans and were silent (barring electronic and drive noise); but PCs were office tools first and foremost, and noise was less of a factor. I think it’s also fair to say that IBM had a tendency to err on the side of caution, favouring sturdier components and designs even if it meant they were noisier. (Later on there were fanless clones, such as the Sinclair PC200.) The push to make cheaper computers, later in the 80s and especially early 90s, didn’t help with noise: cheaply-built and assembled systems often had quite a lot of case buzz, and electronic noise from cheap components wasn’t unusual.

For quite a long time too, fan noise was a minor component in the overall picture: fan noise was constant, as was the whine from hard drives, so it ended up fading into the background, unlike the constant chatter of floppy drives, hard drives seeks, and for those of us unlucky enough to have to print regularly, dot-matrix printers. As far as I remember, in the PC space fan noise became a concern for manufacturers in the late 90s and early 2000s, especially in the race to GigaHertz which led to small, noisy CPU fans and many fried CPUs.

All that racket died down as components improved: floppy drives disappeared, hard drives became quieter (this was an important feature in the early 2000s), cases became quieter, heatsinks got bigger, fans improved and acquired the ability to vary their speed as necessary, and CPUs started taking their thermal envelope into account.

The two computers you mention were presumably representative of their eras. The 1992 PC came just before manufacturers started paying much attention to energy consumption (the Energy Star program started in 1992) or even noise; it would likely have a somewhat noisy PSU, and a whiny hard drive. The late 90s PC came after; it would have benefited (slightly) from improved CPUs with varying power consumption, quieter hard drives, and likely had more than one fan, leading to a lower noise floor than the 1992 PC.

Don’t read too much into CPU evolution though in the context of this question. Microprocessors in the 80s and early 90s didn’t produce enough heat to pose any threat to themselves; however their energy consumption and heat production didn’t drop when they were idle (at least, in desktops). Starting in the mid-90s, x86 CPUs did reduce their heat production when idle, but their thermal envelopes increased dramatically as Intel and AMD raced to produce the first GHz CPU. Since then, idle power consumption has decreased an awful lot so that an idle CPU now doesn’t take much energy at all.

Answer 4

Back then 110/230V fans where common. Later 12V became the norm. I think the higher voltage fans are more noisy.