Question Why does listening to certain PC fans make me drowsy?

[Root602]

I've noticed that with specific fans in my PC, like a Be Quiet fan, I start to fall asleep listening to it. I can try to resist falling asleep, but eventually it happens. Maybe it's due to the white noise, or the pitch, or something. But an Arctic one for example not at all. Why is this the case? Is it because maybe one has thinner blades, is louder, or less loud? What is the factor causing this? I bought a 120mm "Silent" fan from eBay that runs on USB, and while you can definitely hear it and it's pretty noisy, I still fall asleep. Maybe it's because they are silent fans? Maybe silent fans are made different compared to normal ones?

 

[Aeacus]

Sound frequency intolerance would be my guess.

Each fan has it's own sound frequency, measured in Hz, which is completely different from the loudness of noise, measured in dB(A).

Two courses of action;
1. Use those fans who's frequency doesn't affect you.
2. Make a visit to ear doctor who can diagnose your hearing issue and perhaps even determinate the Hz range that makes your body to release melatoin.

Some sound frequencies (humming to say so), has calming effect and releases melatoin, which in turn makes people sleepy. Some people are more acceptable to humming noises than others.

 

[Root602]

Sound frequency intolerance would be my guess.

Each fan has it's own sound frequency, measured in Hz, which is completely different from the loudness of noise, measured in dB(A).

Two courses of action;
1. Use those fans who's frequency doesn't affect you.
2. Make a visit to ear doctor who can diagnose your hearing issue and perhaps even determinate the Hz range that makes your body to release melatoin.

Some sound frequencies (humming to say so), has calming effect and releases melatoin, which in turn makes people sleepy. Some people are more acceptable to humming noises than others.

How can I measure the Hz of a case fan? Is there a meter which can determine this?

 

[Aeacus]

Sound wave frequencies can be measured with a frequency counter or with a spectrum analyzer. These devices work by using a microphone to convert the sound wave into an electrical signal.

Neither of the two are cheap and also require know-how to operate them. E.g identifying the correct frequency from correct source. They are usually used in a sound isolated rooms, so that the ambient noise (frequencies) doesn't mask up the readings.

 

[Misgar]

If you own a smartphone, you could download a spectrum analyzer app.

https://play.google.com/store/apps/details?id=com.raspw.SpectrumAnalyze

https://apps.apple.com/us/app/spectrum-analyzer-rta/id490078884

 

[Root602]

If you own a smartphone, you could download a spectrum analyzer app.

https://play.google.com/store/apps/details?id=com.raspw.SpectrumAnalyze

https://apps.apple.com/us/app/spectrum-analyzer-rta/id490078884

I downloaded the app, and would the peak frequency be the sound of the fan?

Sound frequency intolerance would be my guess.

Each fan has it's own sound frequency, measured in Hz, which is completely different from the loudness of noise, measured in dB(A).

Two courses of action;
1. Use those fans who's frequency doesn't affect you.
2. Make a visit to ear doctor who can diagnose your hearing issue and perhaps even determinate the Hz range that makes your body to release melatoin.

Some sound frequencies (humming to say so), has calming effect and releases melatoin, which in turn makes people sleepy. Some people are more acceptable to humming noises than others.

In one review of the Be Quiet! Silent Wings 3 (my fan) on Amazon, the author stated that it produces a 6hz frequency and another above 19000hz. Here is a link to the review: https://www.amazon.com.au/quiet-BL0...eviews&pageNumber=1&filterByKeyword=dangerous

The problem is you wouldn't be able to see 6hz for example on the graph, it would be so tiny. And the rest of the surrounding frequencies, would make it very hard to see which ones are being produced by the fan using the Spectrum Analyser app on iPhone. Why are fan manufacturers able to get away with producing these fans? Shouldn't there be some kind of standard, so that every fan on the market produces the same Hz? As seeing from that Amazon review 590 people have had the same problem, so this definitely isn't just a few people.

 

[Misgar]

Some historical reading about the effects of 7Hz infrasound from Wikipedia:-
https://en.wikipedia.org/wiki/Infrasound

One of the pioneers in infrasonic research was French scientist Vladimir Gavreau. His interest in infrasonic waves first came about in 1957 in the large concrete building that he and his research team were working in. The group was experiencing bouts of periodic and deeply unpleasant nausea.

After weeks of speculation on the source of the nausea — the team was convinced that it was a pathogen or an untraced leak of noxious chemical fumes in the facility — they discovered that a “loosely poised low speed motor… was developing [these] ‘nauseating vibrations’”

When Gavreau and the team attempted to measure an amplitude and pitch, they were shocked when their equipment detected no audible sound. They concluded the sound being generated by the motor was so low in pitch that it was below their biological ability to hear, and that their recording equipment was not capable of detecting these frequencies.

Nobody had conceived that sound might exist at such low frequencies, and so no equipment had been developed to detect it. Eventually, it was determined that the sound inducing the nausea was a 7 cycle per second infrasound wave that was inducing a resonant mode in the ductwork and architecture of the building, significantly amplifying the sound.

 

[Aeacus]

Why are fan manufacturers able to get away with producing these fans? Shouldn't there be some kind of standard, so that every fan on the market produces the same Hz?

As said in the amazon feedback you linked, Be Quiet! most likely didn't test the Hz range of their fans. Also, it isn't that simple to test either, since if you put a fan inside the PC case, it's Hz range chances. It could very well be, that when fan is tested alone, outside of PC case, it doesn't produce that Hz range, but does when installed in specific orientation in specific case. Or Be Quiet! just didn't test Hz range. Since after all, airflow and static pressure are the two main things to develop/test.

All-in-all, i think the affected people amount is too little for Be Quiet! to test their fans in-depth and/or change the fan design.

I'd be curious to see some scientific research on this.

Yes, it would be, but it would be expensive and takes some time.