What kind of noise is a fan?
A fan is closest to pink noise, not white. Its energy falls away as pitch rises rather than sitting flat, which is why it sounds softer and rounder than the hiss most people picture when they hear "white noise". If you want the full comparison, we went through it in depth.
But a fan is not just noise with a slope on it. The part that makes it a fan is the slow rhythmic sweep as air moves past the blades, somewhere between one pulse every twelve seconds and just over one a second depending on the fan. That sweep is a large part of why people who cannot sleep to plain noise can sleep to a fan.
The seven fans, and when to use each.
Every fan here is defined by two things: where its energy sits in the spectrum, and how fast it sweeps. Those two numbers are what separate a ceiling fan from a desk fan on high, and both are listed so you can see why they sound the way they do.
| Fan | Character | Center | Sweep | Closest to |
|---|---|---|---|---|
| Slow Fan | Gentle, steady | 300 Hz | 0.3 Hz | A desk fan across the room on low. |
| Medium Fan | Richer airflow | 550 Hz | 0.7 Hz | A desk fan at arm's length on medium. |
| Fast Fan | High energy | 900 Hz | 1.3 Hz | A fan on high, close by. |
| Bladeless Fan | Smooth, hum-free | 240 Hz | 0.08 Hz | Air moving through a room with no motor in earshot. |
| Tower Fan | Steady, focused | 500 Hz | 0.15 Hz | A tower fan in the corner of a bedroom. |
| Box Fan | Wide, room-filling | 400 Hz | 0.6 Hz | A box fan in a window. |
| Ceiling Fan | Low, airy drift | 180 Hz | 0.2 Hz | A ceiling fan two rooms' worth of air away. |
A lower center frequency sounds deeper and further away. A faster sweep sounds more urgent and masks a little more. Ceiling and bladeless sit at the calm end, fast sits at the other, and slow is where most people land for a full night.
Do you need a louder fan?
Usually not. When a fan is not covering what is bothering you, the instinct is to reach for a louder one, but volume is rarely the variable that matters. A fan whose energy sits where the disturbance sits will mask it at a far lower volume than a louder fan pointed at the wrong part of the spectrum.
Voices and traffic live in the mid-range, so a medium or fast fan covers them at a volume a slow fan cannot reach. A rumble from a road or a boiler needs the low end, so ceiling or bladeless will do more than turning up a desk fan. This is the practical argument for having seven rather than one: changing fan is usually cheaper than changing volume, and easier on your ears across eight hours.
A rough test that works for all seven: if you would have to raise your voice to talk over it, it is louder than the job requires. The full three-step method is here.
Why a synthesized fan beats a recording.
A recorded fan is a recording of one room. It carries that room's reflections, whatever else was audible that day, and the microphone's own character, and none of that can be removed afterwards. It also has to loop, and a fan's sweep makes the loop point easier to catch than almost any other sound, because your ear is already tracking a rhythm.
A synthesized fan has no room in it and no take. It also has no motor whine, no bearing rattle and no dust, and it does not cool the room down at 4am or stop working in winter. What it keeps is the part you actually wanted: the airflow and the sweep.
How this generator actually works.
Each fan is a live signal chain, not a clip. White noise runs through a bandpass filter that sets the tonal character, then into a gain stage whose level is driven by a sub-1 Hz sine oscillator. That oscillator is the blade sweep, and its rate and depth are what your ear reads as a particular kind of fan.
The seven share one 30 second noise buffer and differ only in those filter and oscillator settings, which is exactly how the app does it. Because the sweep is a live oscillator rather than part of a recording, it never lands on the buffer boundary the same way twice, and switching fans crossfades over a third of a second instead of cutting, so you can compare two of them without a gap in between.
Try the other sounds.
If a fan is not the right texture, the noise colors are a different approach to the same job: white, pink, brown, green and grey, or all five side by side.