Congrats on getting it open and washed!

You didn't explicitly say that you replaced any capacitors, so I'll assume that you didn't. That would explain the whine -- if one of the failed/failing capacitors is in the audio circuit, it can cause various noises. Replacement is the cure. If you're lazy, you can stick a plug into the external speaker jack; that will disable the internal speaker. As long as the noise isn't being emitted by something other than the audio driver, that stopgap measure will silence the beast.

But long term, you'll need to replace the capacitors.