An aversion to making audible noises in the toilet (or hearing those of others) is culturally "normal" in Japan. For this reason many public toilets there play music or running water noises as soon as the toilet is engaged.

What you must realise is that your fears exist only in your own mind - if you start projecting them onto others, i.e. worring about what others will think of you, you will only make things worse by building up your fear until it seems insurmountable.

It sounds like you have managed, albeit uncomfortably, in the same situation previously by turning on the shower. Envisage yourself employing the same tactics again and successfully getting through the weekend - minimise rather than maximise your perception of the difficulties you might face.