I'm looking for a word to describe the sound coming from an air purifier. The purifier sucks in air through a filter, then blows the air back out of its top. The sound is similar to a quietly running air conditioner.
- hum: the sound does not have a tone, it's very airy
- hiss: the sound is not as high-pitched as a hiss
- puff: puff describes a short release of air, but the sound is continuous.
I prefer a single English word, but a word from another language is okay if there is no english word to describe what I hear.