Used to be able to change the sound... yes, the notify.wav file had to be replaced, but at least it was possible. What explanation can Atlassian possibly have for removing our ability to replace that file or modify the notification sound? Reminds me of what Henry Ford did to his employees' prototype when they tried to change it from his perception of the perfect car.
Hipchat is falling miserably behind Slack and other chat clients. Instead of restricting innovation, Atlassian should be encouraging it.