My output sound on my laptop is really quiet however, I cannot change the output volume. Anyway to make my MacBook Air louder?
If you have gone to System Preferences, Audio and everything seems normal, it’s time for a Genius Bar appointment. 

Do not be like me and have all the audio panned to the left (it happened to me more than once and it’s very embarrassing). Ensure your “balance” is centered. Your device list will likely be different (I have a bunch of Audio interfaces) but still, you should have Internal Speakers selected (and maybe as the only option, that’s normal). 

If balance is centered. If output volume is decent and you still can’t hear very well, there may be a hardware malfunction and the Genius Bar is the way to diagnose it.