I just noticed a direct correlation between my happiness level throughout day and whether I sing in the shower that morning. Also, immediately after I step out of a shower singing session, I'm happier than I am when I step out of the shower after a non-singing shower session, regardless of the time of day. Normally, I'm a night-showerer, but lately I've been showering both at night and in the morning, just because showering is so much fun. I think I'll have to choose one or the other for the environment's sake, though.
This picture is from a site called Singing Shower, and there's lots of videos about the acoustics of singing in the shower. The best part? The people in the videos are speaking Hebrew! So, I got to murder two birds with one stone by both learning the proper way to sing in the shower and by getting to brush up on my Hebrew skills. In one of the videos, a woman sings Old McDonald Had a Farm in Hebrew, but still says "e i e i o" in English. Weird.
I couldn't find any studies correlating singing in the shower and happiness, but if I had, I could state that:
*since it's in bold, it's centered, and I used an "=" sign, it becomes the truth.
hahah i like that equation. i used to sing in the shower everyday (as youve heard) but my voice isnt good anymore so i stopped. i wouldnt say im less happier, but maybe im more tense.