The Bonus Bells are small golden bells that hang in a hole above the portals on Challenge Act Gates. Each gate only has one Bonus Bell.
In the console/PC version of Sonic Generations, the Bonus Bell will appear on its Challenge Act Gate when its designated Challenge Act is completed. Sonic must jump into the Bonus Bell in order to release a musical note that gives the player new music tracks or pieces of artwork for the Collection Room.
Once the Bonus Bell has been rung and its musical note has been collected, it turns dull bronze in color.