You create a sound or an image of an object that lasts for the duration. The illusion ends early if you dismiss it as an action or cast this spell again.
If you create a sound, it can be any volume and noise. The sound can continue unabated for the duration, or you can make sounds at different times.
If you create an image of an object, it must be no larger than a 5-foot cube. The image can't create any sensory effects. Physical interaction with the image reveals it to be an illusion.