Wacker Neuson WL36 with noise in the steering

I have a Wacker Neuson wl36 wheel loader with a hydraulic noise in the steering circuit. It is kind of a high pitch vibration noise and is worst at 1700 rpms. It goes away at high rpms and a low rpms. Serial number is 3020274 This is a tier 3 machine. Wondering if this is normal or if there is something I can do about it.