SINGING IN THE SHOWER
Why do we sing in the shower? Clearly we like the sound. But why?
There are several effects that can contribute to this. The first is the high reflectivity of bathroom tiles, which together with the relatively small space, is likely to provide far more feedback of our own voice than would a normal room or, heaven forbid, singing in an open public space. This presents a different perspective of your voice to your usual internal perception, and makes your voice sound more impressively powerful (especially to you).
Second is the reverb effect from multiple reflections as the sound bounces around the usually parallel walls. Singers love the effect of reverb, the long tail-off of sound creating the effect of space and tonal richness, even though the actual bathroom space itself is small.
Thirdly this small room size and usually parallel walls will likely create quite a low resonance, somewhere between 100 and 200Hz. This adds to the richness of the reflected voice.
Finally, of course, there is the confidence-boosting effect of privacy. A closed door and the covering sound of running water may encourage singing, even from those who really shouldn’t.