I could hear both channels in firefox.
Can you try the following?
1) Open your firefox, drag and drop section8_0.ogg directly into a new tab.
2) Play back
3) Are you able to hear both channels ?
nope. still on the left channel. i don't know if it's firefox. i tried researching about this but no results
Looks like a local issue ( with your driver/soundcard/speaker). Can you try in another machine ?
I tried on Firefox v32.0.1, it's playing through both channels.
Seems like browser media play issue.
Can you try two things,
1. Try with some other audio file.
2. Try updating the firefox, and check again.
Let us know your findings.
thank you Siva and Vivekuma! the problem was with my headset. it has an issue with it's soundcard and with firefox.