Hissing noise

What's up guys my gf has a 2004 Scion xB and recently there has been a hissing noise coming from under the hood... it was really faint about a month ago been in the last week or so it's gotten a bit louder... when idling it makes the noise and when you press the gas softly it gets a bit louder... sitting inside the car you can hear it clear as day, but when hood it open it seems tuff to hear from the outside clearly... idk if maybe it's a vacuum hose or something else... any help would be greatly appreciated...

Yes, it is possibly a cracked vacuum hose or bad connection at the end of one. Also, check the intake air hose, air cleaner to throttle body, for leaks/cracks.