When you upload audio files in your app demos it is important to make the files as small as possible so that they'll play on all mobile platforms. Big audio files sometimes won't be played by mobile browsers as these have build-in mechanisms to load web pages as efficiently as possible - and sometimes they'll just choose not to load sounds.
Follow this guide to learn how to compress your audio files.
We'll use Audacity, which is a wonderful free tool for recording and editing audio files - you can download it here: audacityteam.org.
Launch Audacity and open the file you want to compress:
File menu -> Open
File menu -> Export Audio
Click the Options button in the bottom right corner.
Then set the quality to 64kbps
You can experiment with other values, but we found that the 64kbps is the perfect balance between high quality and small file size.
Now you can save your compressed file. You're done!
A 10 seconds audio file should have below 100 Kb. While a one minute audio should stay below 500 Kb.
As long as your audio files are within these ranges your demo should hear great on most modern mobile devices.