smashed phone = broken mic?

so about a couple of days ago i smashed my iPhone 5 for the second time, i just dropped it on a hard floor. I'm planning on getting it fixed like the last time it smashed but this time its different... so I've realised that when i try to record a video with my front camera the sound isn't working when i play it back (its just a muffled sound) but when i record a video on my back camera the sound is fine? the front cameron my phone doesn't have a crack on it. My music and youtube videos etc the sounds working fine for those, its just whenever i try to call someone and when i try to record with my front camera?