B-737 First Officer reported a cockpit window malfunction that resulted in a return to the departure airport. The flight performed a safe overweight landing.

Narrative

I was the Pilot Flying. During the climb out on the ZZZZZ SID at approximately 15;200ft we experienced a window seal issue. I transferred controls to the CA briefly; to allow me to assess where the noise was coming from. I established it was the R2 window - FO side. The noise was so loud and unbearable that hearing one another was extremely difficult especially ATC instructions. We decided to return back to ZZZ. We successfully notified ATC; Dispatch and the Cabin Crew. CA and I; completed the correct QRH procedures and checklists associated with the situation. We knew we would have an overweight landing so we accomplished an overweight landing QRH and landing assessment. Once we were ready and tasks were completed; we asked for vectors for a visual approach to Runway XX. On short final; we got an aural warning 'TOO LOW TERRAIN' 4/5 times. I continued my landing as I was stable; making any changes/adjustments at that point would not have been beneficial. A smooth; overweight precautionary landing was successfully accomplished. After exiting the runway safely at Taxiway 1; I organized for an open gate with Ramp/Ops. At the gate we completed the shutdown checklist and began liaising with our Dispatcher and Maintenance team to make necessary Logbook entries and co-ordinate an aircraft swap so we could continue on to ZZZ1.Cause: A new hire employee was conducting the windshield clean while I was downstairs doing the pre-flight. Captain was in the cockpit loading FMS while observing the windshield clean. I believe the way the window may have been closed; played a role in the unbearable noise we experienced. Also... On short final despite completing the Before Landing Checklist flaps were left in the 25 degree position. I believe this was overlooked due to distraction of noise and task saturation. My situational awareness at that point was solely on remaining stable and getting the aircraft down safely. Suggestions: To ensure the correct training is given to anyone who is cleaning the flight deck windshields. Pay closer attention to the flap indicator once flap handle is moved - continue to verify this in my scan.