As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTS, LOUD AIR NOISE IN RIGHT SIDE OF CABIN ROW 15. AIR SYNOPTIC SHOWS RIGHT PACK WITH NO FLOW. RIGHT DUCT PRESSURE NORMAL. AIRCRAFT RETURN TO ORD (ORD-LHR). *S/D* SUSPECT NO FLOW INDICATION ON SYNOPTIC PAGE RESULT OF STICKING FLOW CONTROL VALVE (PN 810204-2) PROXIMITY SWITCH (PN 808577-2). ALSO, REPLACED CABIN TEMPERATURE CONTROLLER PRECAUTIONARY.