Eliminate background noise in home made videos
Forget an app. The truth is that a mic is, not only the best option but also an honest option. It will help the audience to focus on the content instead of making it a pain to hear.

I would go for a cable lavalier mic, there are some in amazon, and they are the cheapest alternative.

https://www.amazon.com/s?k=cellphone+microphone

The other option is a shotgun mic, but they are a bit more expensive, and normally are for outdoor usage and for interviews for example. For one person a lavalier is the best alternative.

You could also try a "hands-free" earphone with a mic. Probably your cellphone came with one already.



Why a lavalier?

The way a lavalier mic reduces the ambient noise is... It does not.

But the ratio of the proximity to your mouth, let's say 10cm or 4in to any other source of a sound, a fan, that can be 2mts away is 20 times the distance. And depending on the echo of the room, this difference could make the sound less prominent by one law that is the inverse square law that makes this difference exponential.

But if you have your camera at let's say 2m away from you, using the internal mic, and the fan is above you, the ratio of distances is probably only 1.5 times. So when you record your voice, you need to pump the volume, therefore you also pump the volume for the fan.



Hands-free is not the same as Bluetooth. There are cable options.

Regarding a blue tooth or not, I can not recommend anything. Bluetooth has the risk of having some delay, or not. If that is not important, because you are not showing the face it is ok. But this depends on the model or brand. I suppose if you buy one Bluetooth hands-free for some brand it would recognize that device.

Cable or Bluetooth is just a way to connect a device. That is up to you and you need to make some homework to see if the device fits your phone.

But normally a lavalier mic is expected to have better sound quality than mic on a hands-free device. Of course, depends on the brand.

Some cable lavalier mics need batteries, make sure to buy some extra. Also, check the length of the cable.

You could add some cable extension, but that is not recommended because you could add electronic noise into the signal, but you could try. The not so cheap option is a lavalier with a UHF transmitter.