It's not a flaw, just need to check two things:
1. Make sure your volume is turned UP
2. Be sure your device's ringer is turned on. If vibrate mode is on, the sound will not play for videos, or audio players.
This may seem simple, but it's a very common oversight :) If this troubleshooting does not fix the issue, please feel free to shoot us an email at firstname.lastname@example.org