when it makes this sound, and how long? is it a prime? under warranty? maybe the brake actuator, hvac, or coolant pump
My first thought, too. Sounds like a stick got sucked in through the vent openings. They can really pile up there under the hood.
35k miles, not prime out of warranty. Makes the noise for about a min after turning the car on,but not every time. Gets louder when accelerating.
To my Untrained ears it sounds like one of the HVAC mode motors is jammed and it's skipping teeth in the small gearbox b/c of the jam. As said above, might be a stick or other foreign matter jammed above the blower motor as thats usually where the recirculate/fresh outside air motor is.