To adjust the sound that you will hear on your Jobulator application, you will need to go to the "Settings" tab of Jobulator and tap Job Notification Sound.
This opens a new page where you can adjust your notification settings. Choose the Sound option to select a new notification sound.
Please note that if you choose a sound file from your phone to play for new jobs, the Media volume will need to be turned up as well. For more information, consider referencing this article on important Android settings.