Cricket under my hood

Have a cricket noise under my hood that only occurs at 35-40mpg. Just paid for installation of new tensioner and timing belt, and had alternator replaced. Any idea what this noise is?

Please Make It Clear That The Noise Began After The Maintenance Work Was Done And That The Work Wasn’t Done To Remedy A Noise.

Also, was the serpentine belt or any accessory belts replaced or were the old ones reinstalled ?

After-market alternator ? I’d put a straight edge on the face of the alternator pulley (with the engine off, of course) and make sure that this pulley aligns (is on the same plane) as the other pulleys, including crankshaft, tensioner, etcetera.

Are you going back to have it checked ?

Does the noise go away if you lightly depress the brake pedal ?

What model-year is this Kia Optima ?
Any time we’re talking about engines, we’d like to know which engine you have.