Can't play audio files through my email while I use another app

I want to start by saying thank to whomever takes the time to respond. Recently, I decided it was time to upgrade to IOS 9.2.1, the notifications were getting really annoying. I send and receive many audio files to my personal email, which I have on my phone. I usually play the file, then switch apps, but now I can't do that because every time I press the home or lock buttons, the file stops playing. I was wondering if there was a way to set it so the file can play in the background again?