Hi there ! My English is not so good but I will do the best I can. Hope you guys will be better than my mechanic...

I have a 2013 Fit LX since a few months. There's a strange noise that no one can explain. It's like an audio white noise going on intermittently for a few seconds every minutes. It's going on only when I drive and only when the fan is on, cooling or heating. When it starts and I turn off the fan, it immediatly stops... My air filters seems to be OK, and it's not a rattling sound. More like ssshhhh ing sound...

Really strange to me.
Thanks !