Recording audio without background noise

[crystal_bannon]

I like to take my phone to concerts to take pictures and record video. Unfortunately I also record all the background noise, people singing mostly (including myself sometimes). I was hoping there was an accessory that would snap/wrap around the bottom of the phone that would block the audio from that side - so when I am looking at what I'm recording there is something extra (plastic??) that extends from the bottom. Maybe I'm crazy but I can't be the only one who has thought of this, I just can't seem to find one online for sale. Is this even possible? Where should I be looking?